American History Chronologically is built on 10,773 entries written for this project and on the original records listed here: laws, treaties, court decisions, census counts, and the histories kept by the agencies responsible for them. Where a page rests on estimates, or leaves something out, this page says so.

Timeline

Entries. The American History Chronologically dataset, version 1.2, written for this project from year-by-year research across the 25 topics the timeline is divided into.

Eras. The project's own framework: 51 historical eras, and four deep-time eras from the forming of the continent to the megafauna the first people met. The Megafauna Baseline is set to begin about 130,000 years ago, with the last full glacial cycle. Where one era begins inside a longer one, the later era takes over the line from its start.

Sovereignty

Claims, purchases, and cessions. The treaties and acts that made them: the Treaty of Paris of 1783, the Louisiana Purchase treaty, the Adams–Onís Treaty, the annexation of Texas, the Oregon Treaty, the Treaty of Guadalupe Hidalgo, the Gadsden Purchase, the purchase of Alaska, the joint resolution annexing Hawaii, and the Treaty of Paris of 1898, as held by the National Archives and described by the State Department's Office of the Historian.

Native sovereignty. Eras from the project's framework, marked by federal laws such as the Indian Removal Act of 1830 (Library of Congress) and the Dawes Act of 1887 (National Archives).

Government

Elections: electoral votes and notes for every election from the National Archives, Electoral College Results; popular vote shares, which no federal agency compiled before 1920, from the American Presidency Project at the University of California, Santa Barbara.

Impeachments and attacks. The marks along the presidents' row on Leaders: the four presidents impeached by the House, all acquitted by the Senate, and Nixon's resignation ahead of a vote, from the House Historian's list of impeachments; the four presidents assassinated and the attempts on Jackson, Theodore Roosevelt, Franklin Roosevelt, Truman, Ford, Reagan, and Trump, from the National Archives and the presidential libraries.

The Cabinet. Every department in the order Congress created it, which is also the line of succession, seventeen lanes, by year of service; War and Defense share a lane, since Defense took War's place in 1947. State from the Office of the Historian; Treasury from the Treasury Department; War from the Army Center of Military History's Secretaries of War and Secretaries of the Army; the Navy from the Naval History and Heritage Command; Postmasters General from the Postal Service's list; Interior from its museum's record; Agriculture, Commerce, Labor, Health and Human Services, Housing and Urban Development, Transportation, Energy, Education, Veterans Affairs, and Homeland Security from each department's own list of former secretaries; Defense from the Historical Office of the Secretary of Defense; attorneys general from the Justice Department's Attorneys General of the United States. Acting secretaries are not shown.

First ladies. National Park Service, First Ladies National Historic Site, First Ladies of the United States, which includes the relatives who served as hostess for unmarried or widowed presidents. Running mates and their electoral votes come from the same National Archives election pages as the presidential results.

Presidents. Office of the Historian, U.S. House of Representatives, Presidents, Vice Presidents, and Coinciding Sessions of Congress. Where a president died in office, the successor's term starts on the day of the death rather than the oath taken a day or two later. The page runs to January 2033: the current terms are shown to their scheduled ends, and the Congresses and presidency still to be decided by the elections of 2026, 2028, and 2030 are left unknown.

Vice presidents. United States Senate, Vice Presidents of the United States, for each vice president's party and the dates of every death, resignation, and succession that left the office vacant, with term start dates from the House list of presidents and vice presidents above.

House. Office of the Historian, U.S. House of Representatives, Party Divisions of the House of Representatives, 1789 to Present. Each Congress is stacked by its party split rather than shaded for the majority alone, with Democrats and their forerunners on top and Republicans, Whigs, and Federalists below.

Speakers. Office of the Historian, Speakers of the House by Congress and Speakers in numerical order, including the dates of each death, resignation, and removal and each Speaker's total days in office.

Senate. United States Senate, Party Division. Majority leaders from the Senate Historical Office, Majority and Minority Leaders, which traces party floor leaders to about 1890; the posts were formally designated in the 1920s, and the Senate had no equivalent to the Speaker before then.

Supreme Court. Supreme Court of the United States, Justices 1789 to Present. The top lane is the chief justice's seat, set off by a rule; the lanes below follow the associate seats as each passes from justice to justice. Every justice is colored by the party of the president who appointed them, so the three who rose from associate to chief appear twice, once in each seat. Associate seats are traced by succession, showing who followed whom rather than the Court's own numbering.

Founding documents and amendments. Full texts from the National Archives transcripts of the Declaration of Independence, the Articles of Confederation, the Constitution, the Bill of Rights, and Amendments 11 to 27. The six amendments Congress passed that the states never ratified follow the Congressional Research Service, Proposals to Amend the U.S. Constitution: Fact Sheet (R47959), with their texts as Congress sent them to the states. The original's dashes are shown as double hyphens, as the Archives does in its own transcripts.

States

Admission dates and the laws creating each territory from the Congressional Research Service, Admission of States to the Union: A Historical Reference Guide (R47747, 2023), which cites the admission and territorial acts in the Statutes at Large. Colony and earlier start dates show the year only. Territories, the District of Columbia, and former territories follow the Interior Department's Office of Insular Affairs (American Samoa, Guam, the Virgin Islands, and the Northern Mariana Islands, with the Trust Territory), the State Department's Office of the Historian on the Spanish-American War and the Panama Canal (1903 and 1977), Proclamation 2695 recognizing Philippine independence, and the National Archives on the Platt Amendment for Cuba and Guantánamo Bay. Secession dates are those of each state convention's ordinance of secession, or for Tennessee, the popular vote that approved it. Readmission dates are those of the acts of Congress restoring each state's representation, found in the Statutes at Large (for example, Virginia's act of January 26, 1870 and Arkansas's of June 22, 1868). For the five states restored under the act of June 25, 1868, it is the date each ratified the Fourteenth Amendment, as that act required, recorded in the House Manual; Florida, which had already ratified, was restored on the act's own date.

Population

Life expectancy from the CDC's National Center for Health Statistics: its death rates and life expectancy at birth for 1900 to 2018, and its annual Mortality in the United States reports since. The largest cities from the Census Bureau's Population of the 100 Largest Cities, 1790 to 1990, and the 2000, 2010, and 2020 censuses.

Totals. U.S. Census Bureau decennial counts from 1790 to 2020, and the 2024 national estimate. Colonial figures are estimates from the Census Bureau's Historical Statistics of the United States, Colonial Times to 1970.

Native people. Before the 1890 census, a central estimate with the range of published scholarly estimates, not a count.

Born abroad. Census Bureau, Historical Census Statistics on the Foreign-Born Population, 1850 to 2000, and the American Community Survey for 2010 and 2023.

Ethnicity. Census Bureau, Historical Census Statistics on Population Totals by Race, 1790 to 1990, and by Hispanic Origin, 1970 to 1990, including its tables splitting each group into Hispanic and not Hispanic, and the Census Bureau's national tables for 2000, 2010, and 2020. Groups follow the census's own categories, which changed over time. For 1970, the 179,127 Hispanic people among the smaller groups were divided among them proportionally.

Urban and rural, median age, men and women. Census Bureau historical tables and census reports from 1990, 2000, and 2020. The definition of urban was broadened in 1950 and again in 2020.

War

American military deaths from the Department of Veterans Affairs, America's Wars, drawn from Defense Department records; for Iraq and Afghanistan, the Defense Department's casualty reports; for the Iran war, the Congressional Research Service.

Declared wars begin on the dates of Congress's declarations, as recorded by the U.S. Senate in Declarations of War, or with the first fighting where it came earlier, as on the Rio Grande in April 1846. They end with their treaties and armistices. Undeclared wars and the Indian Wars are compiled for this site from military histories; long conflicts, such as the Apache Wars, carry conventional dates. Current conflicts follow the Congressional Research Service, such as its U.S. Conflict with Iran. Each war is colored by its kind, from wars against Native nations to interventions and occupations, and drawn thicker if it was a major war.

Slavery

Enslaved and free Black population. Census counts from 1790 to 1860 (Census Bureau Working Paper 56, above, and the 1860 census report), with colonial estimates from Historical Statistics of the United States before 1790.

Colonies, states, and territories. The constitutions, laws, and court decisions that set each date: the Vermont constitution of 1777; the Quock Walker cases in Massachusetts, 1781 to 1783; Pennsylvania's Gradual Abolition Act of 1780; the gradual abolition acts of Connecticut and Rhode Island (1784), New York (1799 and 1817), and New Jersey (1804); the Northwest Ordinance; Maryland's constitution of 1864; Missouri's ordinance of emancipation and Tennessee's constitutional amendment, both of 1865; West Virginia's abolition act of 1865; Utah's Act in Relation to Service of 1852; New Mexico's slave code of 1859; California's Act for the Government and Protection of Indians of 1850; the Peonage Act of 1867; and the 1866 treaties with the Cherokee, Choctaw, Chickasaw, Creek, and Seminole nations. Start years come from each colony's earliest laws and records of enslaved people and are approximate before 1700. They were checked against the records and the state and federal institutions that keep them: Governor John Winthrop's journal for Massachusetts in 1638 (quoted by the City of Boston); New York State's Office of Parks, Recreation and Historic Preservation, following new research dating the first arrival in New Amsterdam to August 29, 1627; the National Park Service for Delaware and Florida; the Maryland State Archives; Portsmouth's Black Heritage Trail for New Hampshire; the South Carolina Encyclopedia; the New Georgia Encyclopedia and the Georgia Archives; and the Louisiana Endowment for the Humanities' 64 Parishes for the first slave ships to French Louisiana in 1719. Later ratifications of the Thirteenth Amendment, such as Delaware's in 1901 and Kentucky's in 1976, are from the House Manual. For the Confederate states, wartime emancipation runs from the Emancipation Proclamation to the Thirteenth Amendment's ratification, since freedom arrived at different times as the Union army advanced.

Turning points. From the National Archives: the Missouri Compromise, the Kansas–Nebraska Act, Dred Scott v. Sandford, the District of Columbia Compensated Emancipation Act, the Emancipation Proclamation, General Order No. 3 (Juneteenth), and the Thirteenth Amendment.

Women's Suffrage

State laws before 1920. Each date on this page was checked against the state chapters of History of Woman Suffrage, volume 4 (1902) and volume 6 (1922), edited by Susan B. Anthony and Ida Husted Harper, which record each state's suffrage laws as they passed. Kansas's school vote comes from its state constitution of 1859, as described by the Kansas Historical Society. See also the University of Washington's Mapping American Social Movements Project, Timeline and Map of Woman Suffrage Legislation State by State, 1838 to 1919 (Katie Anastas). The page shows the main statewide rights; some cities and counties granted local voting rights that are not shown.

Ratification. The Nineteenth Amendment (National Archives), and each state's ratification, including those decades later, as recorded in the Constitution annotations of the House Manual.

After 1920. The Indian Citizenship Act of 1924, the repeal of Chinese Exclusion in 1943, and the Immigration and Nationality Act of 1952, in the Statutes at Large; the Twenty-fourth Amendment; and the Voting Rights Act of 1965.

Armed forces

Military personnel on active duty at the end of each year. From 1789 to 1970 the figures are the Census Bureau's Historical Statistics of the United States, series Y 904, read from the scanned table and checked against the Defense Department's Selected Manpower Statistics, which reprints the same series; a few years the scan could not be read are left as gaps. Since 1971 the figures are the Defense Manpower Data Center's end strength by fiscal year. The branches are shown for the years the record separates them: the scan's Army, Navy, and Marine Corps columns where they add to the printed total, the Department's tables for 1916 to 1974, and the Manpower Data Center's figures at each census since 1980. The Coast Guard, which serves under the Treasury, Transportation, and now Homeland Security departments except in wartime, is shown at the points its historian's office gives: 10,544 in 1939, 171,749 in February 1944, 171,931 in 1945, 23,000 after demobilization in 1946, and 40,558 in 2020. The Space Force's strength since 2020 is the Air Force's figure. All counts are active duty; the National Guard and Reserve are included only when called to active duty. The draft eras follow the Enrollment Act of 1863, the Selective Service Acts of 1917 and 1940, and the Selective Service Act of 1948, which lapsed in 1973.

Veterans

Veterans living in civil life at June 30 of each year from 1865 to 1970, from Historical Statistics of the United States, series Y 957, read from the scanned table; then the count of veterans at the censuses of 1980, 1990, and 2000 and in the American Community Survey for 2010, 2020, and 2023. The share of population divides by the census total, interpolated between censuses.

Nuclear weapons

The stockpile is the number of warheads, active and inactive, at the end of each fiscal year, as declassified by the government: the years from 1945 to 1961 released by the Energy Department in 1993, and 1962 to 2023 from the Energy and State Departments' Transparency in the U.S. Nuclear Weapons Stockpile fact sheets. Retired warheads awaiting dismantlement are not counted. The two bombs used, at Hiroshima on August 6, 1945, and Nagasaki on August 9, are marked on both views, with the yields and the death tolls as the Energy Department's history of the Manhattan Project gives them. Tests are from the Energy Department's register United States Nuclear Tests, July 1945 through September 1992 (DOE/NV-209), which lists 1,054 tests; the 24 joint tests with the United Kingdom are left out of the yearly counts here.

Native Nations

The eras and the acts that mark them come from the statutes themselves, cited on each card by their place in the Statutes at Large. The count of tribes today is the Bureau of Indian Affairs notice Indian Entities Recognized by and Eligible To Receive Services, published January 30, 2026. The treaties are those printed in Charles J. Kappler's Indian Affairs: Laws and Treaties, volume 2, the Government Printing Office's 1904 compilation, as digitized by Oklahoma State University, matched to the National Archives' ratified treaty numbers.

Expeditions

Thirty-one expeditions sent by the government, from Lewis and Clark to the bathyscaphe Trieste, each drawn from departure to return. The dates, leaders, and routes follow the agencies that sent them and keep their records: the National Park Service for Lewis and Clark, the Army and its Corps of Topographical Engineers for Pike, Long, Frémont, Emory, the railroad surveys, and Greely, the Navy's history office for Wilkes, Perry, the polar voyages, Nautilus, and Trieste, the Geological Survey for the four great surveys and Powell, and the Library of Congress for the early river expeditions.

Flight

Twenty-eight dated events in American aviation, from the Wright brothers' first flight to the FAA's drone rules, in five kinds: first flights and records, aircraft, airlines and air mail, the military, and law. The dates and facts follow the Smithsonian's National Air and Space Museum and the FAA's history of its own predecessors and acts.

Space

Programs, crewed flights, crews, and robotic missions follow the NASA History Office and NASA's mission pages. Every crewed flight is drawn through Apollo–Soyuz; the Shuttle's 135 flights and the Station's expeditions are represented by their milestones.

Political movements

Twenty movements, each drawn from its first organization to the law, amendment, or decision that was its landmark, or to today where it has none yet. The endpoints are the dates of the founding records and of the statutes, amendments, and court decisions named on each card; the choice of what counts as a movement's beginning and its victory is the site's, and each card says which were chosen.

Representation in Congress

Members of Congress in each group, counted Congress by Congress from the rosters kept by the House Historian's office: women, Black Americans, and Hispanic Americans, with delegates and resident commissioners counted alongside the House. Asian and Pacific Islander Americans follow the Congressional Research Service's report on Asian Pacific Americans in Congress through the 113th Congress and its profiles of each Congress since. Native Americans are the members identified as such in the Biographical Directory of Congress, from Charles Curtis in 1893, with the recent Congresses from the CRS profiles; that list is the site's compilation and may miss members of Native descent the directory does not note.

The Asian and Pacific Islander series runs one Congress behind the other four: it ends with the 118th Congress (2023–25), while women, Black, Hispanic and Native American members are counted through the 119th (2025–27).

The Presidency

Vetoes are the Senate's table of vetoes by president, regular and pocket, with the number Congress overrode. Pardons and commutations are the Justice Department's clemency statistics from the Office of the Pardon Attorney, whose tables run from Truman, with the pardon counts for McKinley through Franklin Roosevelt from the office's earlier table for 1900 to 1945 as the department has published them; commutations for those years are still to be added. For the presidents before 1900 there are no official statistics, so the page shows every act of clemency together, from the political scientist P.S. Ruckman's compilation of the Attorney General's annual reports and the presidents' papers, United States Presidential Orders of Clemency, 1789 to 2017 (ICPSR study 37128), drawn hatched so it is not mistaken for the department's split count. Executive orders follow the Federal Register's numbered series: the Archives' disposition tables give each president's range from Hoover on, the Register's own counts cover the presidents since 1994, and the unnumbered orders before Lincoln follow the American Presidency Project's tally of the same series.

Parties

Twenty-eight parties and caucuses, from the Federalists to the Working Families Party, each drawn from its founding to its end. Major parties are full bars, third parties slimmer ones, and the two caucuses that run their members inside a major party are hatched. The years follow the House Historian's party divisions and the Senate Historical Office; each party's best showing is taken from the National Archives' election results used on the Elections page.

Electoral College

Each state's electors in every election since 1792 come from the National Archives' election results pages, the same pages behind the Elections page; the totals for every election match the Archives' published counts. States are grouped by the Census Bureau's four regions.

Education

The share of adults 25 and over who had finished high school, and who had finished four years of college or more, each year since 1940, from the Census Bureau's table A-1 of educational attainment, which begins with the 1940 census, the first to ask.

Income and poverty

All three views come from the Census Bureau's Current Population Survey, its Annual Social and Economic Supplement, which has asked households about the past year's income every March since 1948. Poverty is the official poverty measure, from the historical poverty tables 2 and 3, 1959 to 2025: a household counts as poor if its cash income before taxes falls below a threshold set for its size and raised each year with prices. That measure leaves out taxes, tax credits, food assistance, and housing aid, so it does not show what those programs did; the Census Bureau's newer Supplemental Poverty Measure, which begins in 2009, counts them. Income shares are table H-2 and the Gini index table H-4, both 1967 to 2025. Households are sorted by income and cut into five equal groups, so the five bands always add to a hundred. The survey's income questions were reworked in 1993 and again in 2013, and the 2020 collection was disturbed by the pandemic, all of which the Census Bureau footnotes; the series is shown unbroken because the Bureau publishes it that way.

Health

Life expectancy at birth is the National Center for Health Statistics' series Death rates and life expectancy at birth, 1900 to 2018, with the years since from its National Vital Statistics Reports. The leading causes at each decade from 1900 to 1990 are the Center's compilation Leading Causes of Death, 1900–1998, in the transcription published by Our World in Data, checked against the original for 1900 and 1990; 2000 and 2010 are the Center's leading causes of death file, converted to deaths per 100,000 of the census population; 2020 is the Center's report for that year. All rates are crude, not adjusted for age, so the aging of the population is part of what the columns show.

Births. Live births and the general fertility rate, births per 1,000 women ages 15 to 44, come from the National Center for Health Statistics: its series Births and General Fertility Rates, United States for 1909 to 2018, and Births: Final Data for 2024 (National Vital Statistics Reports, volume 75, number 2, June 2026) for the years since. The figures for 1909 through 1958 are adjusted by NCHS for births that went unregistered: birth registration was not complete in every state until 1933, and those years are drawn hatched. Birth rates by age of mother are the same office's Birth Rates for Females by Age Group, 1940 to 2018, continued to 2024 from table 2 of the 2024 report. The eight age rates added and multiplied by five give the total fertility rate, the children a woman would have if she lived through her childbearing years at that year's rates, which is how NCHS computes it; the stacked chart is drawn that way, and the figures it produces match the published rates exactly.

Home and family

All three series are the Census Bureau's: median age at first marriage from table MS-2, which reaches back to 1890; people per household from table HH-6 from 1940, with the decades from 1790 from Historical Statistics of the United States, series A 335; and the homeownership rate from the decennial housing tables by decade from 1890 and the Housing Vacancy Survey each year from 1964.

Work

Three official counts, kept apart because their categories differ. By industry: gainful workers at each census from 1820 to 1930, from the Census Bureau's Historical Statistics of the United States, series D 152–166, in which only farming is separated before 1870; and full- and part-time employees by industry each year from 1998, from the Bureau of Economic Analysis' national accounts, table 6.4D, as a share of domestic employment. By occupation: the labor force by major occupation group at each census from 1900 to 1970, from Historical Statistics series D 182–198, read from the scanned table with each decade's groups checked against its printed total. The years from 1940 to 1997 by industry are still to be added from the Bureau of Labor Statistics.

Prisons

The imprisonment rate is the Bureau of Justice Statistics' count of sentenced prisoners under state and federal jurisdiction for every 100,000 residents at the end of each year, from its bulletins Prisoners 1925–81, State and Federal Prisoners, 1925–85, the annual Prisoners in bulletins since, and Prisoners in 2023. Jails are not included. Executions are from the Bureau's Capital Punishment, 2023, which counts every execution under civil authority since 1930.

Immigration

People granted lawful permanent residence, from the Department of Homeland Security's Yearbook of Immigration Statistics: table 1 for arrivals each year since 1820, and table 2 for each decade by region of last residence. The Western Hemisphere is shown in its parts as the yearbook gives them: Canada and Newfoundland, Mexico, the Caribbean, Central America, South America, and a small remainder. These counts are of people who received legal permanent status, which is not the same as everyone who arrived.

Economy

Recessions are the business cycle dates of the National Bureau of Economic Research, which has dated every peak and trough since 1857. Unemployment is the Bureau of Labor Statistics' Current Population Survey rate, series LNS14000000, averaged over each year; consumer prices are its consumer price index, series CUUR0000SA0. Federal debt outstanding at the end of each year comes from the Treasury Department, and income tax bracket rates from the IRS Statistics of Income historical table 23.

GDP. Real gross domestic product and real GDP per person, both in 2017 dollars, from the Bureau of Economic Analysis' national income and product accounts (tables 1.1.6 and 7.1), which begin in 1929.

Revenue. Federal receipts by source. From 1934, individual and corporate income taxes, social insurance taxes, excise taxes, and other receipts, from the Office of Management and Budget's Historical Table 2.1. From 1866 to 1933, customs duties, internal revenue, and other receipts from the Census Bureau's Historical Statistics of the United States, series Y 352–357, for the 27 years whose printed figures could be read and checked against their totals; the rest of that table, and the years from 1789, are still to be transcribed.

Spending. Federal outlays by function from 1940, from the Office of Management and Budget's Historical Table 3.1, all eighteen functions, with each function's subfunctions from 1962 from Table 3.2. Undistributed offsetting receipts are left out, so the functions add to gross outlays. The agency view sums outlays by bureau from OMB's Public Budget Database, the account-level file behind the Budget Appendix, for forty-two bureaus and agencies from 1962. All dollar figures are adjusted to 2025 by the change in consumer prices shown on the Prices view.

Trade. Exports and imports of goods on a balance-of-payments basis from 1960, from the Census Bureau's U.S. Trade in Goods and Services series, adjusted to 2025 dollars; the years before 1960 are still to be added from Historical Statistics. The tariff rate is duties collected as a share of imports, from the U.S. International Trade Commission's table of imports, duties, and ratios, 1891–2025; the commission cautions that the ratio measures what was collected, not how restrictive the tariff was, since goods kept out entirely collect nothing.

Unions. Two official series that do not splice. From 1930 to 1970, union members as a share of nonagricultural employment, from the Census Bureau's Historical Statistics of the United States, series D 952. From 1983, when comparable survey data begin, union members as a share of wage and salary workers, from the Bureau of Labor Statistics' Union Members releases. The years between are left blank rather than estimated.

Energy. Primary energy consumption by source, in quadrillion Btu, from the Energy Information Administration's Monthly Energy Review: Table 1.3 for every year from 1949 (coal, natural gas, petroleum, nuclear, hydroelectric, geothermal, solar, wind, and biomass, the last taking in wood, waste, and biofuels), and Appendix D, Table D1, for the estimates before that, which run every ten years from 1635 and every five from 1850 through 1945. The early wood figures are fuelwood only, converted from the Department of Agriculture's count of cords burned, and each decade's average is placed at its middle year; coal, oil, gas, and hydro before 1949 come from Energy in the American Economy, 1850–1975. No estimate exists for 1946 through 1948, and the chart says so where it crosses them. Electricity traded across the borders, never more than a fraction of a percent, is left out.

Public Lands

National forests and grasslands from the Forest Service's Establishment and Modification of National Forest Boundaries and National Grasslands: A Chronological Record, 1891-2012, with the current list of units from its Land Areas Report. Its monuments, recreation areas, scenic areas, and Grey Towers National Historic Site come from the Forest Service's table of congressionally designated special areas, with the proclamations for monuments designated since. How much land the federal government owns, by agency, comes from the Congressional Research Service's Federal Land Ownership: Overview and Data, which compiles each agency's own acreage reports. The Smithsonian's museums and the National Zoo follow the Smithsonian Institution Archives' chronology for founding and opening years, and the Smithsonian's list of museums for the newest. Marine sanctuaries come from NOAA's Office of National Marine Sanctuaries, including its table of sanctuary designations and expansions; the five marine national monuments come from their presidential proclamations. The Bureau of Land Management's monuments, conservation areas, and similar designations come from its detail table of National Monuments, National Conservation Areas and Similar Designations, with each unit's proclamation or public law. The national grasslands were designated under the Bankhead-Jones Farm Tenant Act.

Every unit of the National Park System, from the Park Service's own records: its list of the 433 units by type, the legal history of each unit in The National Parks: Index 1916-2016, and its record of recent changes for units added or redesignated since. Units that left the system come from the Park Service history office's Former National Park System Units: An Analysis by Barry Mackintosh, which covers every divestiture from 1930 to 1994, and the Park Service's article on abolished national monuments.

Current parks. Establishment dates and earlier protection from the National Park Service, The National Parks: Index 2012–2016, and for parks designated since, their establishing laws in the Statutes at Large, such as the Gateway Arch National Park Designation Act of 2018. Where the index and a law differ, the law's date is used. Each park links to its page on nps.gov.

Former national parks. The same Park Service index for the six still in the park system: Platt, Abraham Lincoln, Fort McHenry, General Grant, Rock Creek Park, and Hawaii. Mackinac State Historic Parks for Mackinac, and the U.S. Fish and Wildlife Service for Sullys Hill.

Turning points. The act establishing Yellowstone (National Archives), the Antiquities Act, and the Organic Act of 1916 creating the National Park Service.

Media

Two hundred seventy-three movies, television series, and documentaries that tell the story of America, each drawn across the years it depicts rather than the year it was made. The list, the notes on faithfulness, and the era assignments are the site's own research; the scores are from IMDb, Rotten Tomatoes, and Metacritic as checked in September 2026 for the recent titles and the pre-contact documentaries, with older titles' scores recalled rather than re-checked and marked "not verified" where they were not. Alternate-history and fictional-universe works are left out. The Plays, Books, Music, Art, and News pages follow the same rule, each work across the years it depicts (a newspaper across the years it published), without scores; the lists are the site's own, and the Library of Congress's National Recording Registry, its Books That Shaped America, and the Pulitzer Prizes are to be added as frames when their sites allow the download.

Lifespans

The birth and death entries in the dataset, matched by name.

Spot an error? Corrections are welcome through megatheriumclub.org.