| The Colonial Era | |
| 1492-1493 | First transatlantic voyage of Christopher Columbus |
| 1493-1496 | Second transatlantic voyage of Christopher Columbus |
| 1497 | English explorer John Cabot reaches the North American coast |
| 1498-1500 | Third transatlantic voyage of Christopher Columbus (Columbus returns as a prisoner in chains) |
| 1501-1504 | Fourth (and final) transatlantic voyage of Christopher Columbus |
| 1587 | First English colony in North America on Roanoke Island |
| 1607 | First permanent English colony in North America at Jamestown on Chesapeake Bay |
| 1620 | Plymouth Colony |
| 1774 | First Continental Congress |
| The Revolutionary Era | |
| 1775-81 | American War of Independence |
| 1776 | Declaration of Independence |
| 1781 | Articles of Confederation |
| 1783 | Treaty of Paris |
| 1787 | The United States Constitution |
| 1787 | Delware (December) |
| Pennsylvania (December 12) | |
| New Jersey (December 18) | |
| 1788 | Georgia (January 2) |
| Connecticut (January 9) | |
| Massachusetts (February 6) | |
| Maryland (April 28) | |
| South Carolina (May 23) | |
| New Hampshire (June) | |
| Virginia (June 25) | |
| New York (July 26) | |
| 1789 | North Carolina |
| 1790 | Rhode Island |
| The Early Republic | |
| 1791 | Vermont |
| 1792 | Kentucky |
| 1796 | Tennessee |
| 1803 | Ohio (March 3) |
| Louisiana Purchase (April 30) | |
| 1804 | Lewis and Clark Expedition |
| 1812-15 | The War of 1812 |
| 1812 | Louisiana |
| 1814 | Treaty of Ghent (December 24) |
| 1816 | Indiana |
| 1817 | Mississippi |
| 1818 | Red River Purchase |
| Illinois (December 3) | |
| 1819 | Spain cedes Florida to the United States |
| Alabama (December 14) | |
| 1820 | The Missouri Compromise |
| Maine | |
| Missouri | |
| 1836 | Arkansas |
| 1837 | Michigan |
| 1845 | Florida (March 3) |
| Texas (December 29) | |
| 1846-48 | Mexican War |
| 1846 | Oregon Territory (June) |
| Iowa (December 28) | |
| 1848 | Treaty of Guadalupe Hidalgo (February 2) |
| Wisconsin (May) | |
| 1850 | California |
| 1853 | Gadsden Purchase |
| 1858 | Minnesota |
| 1859 | Oregon |
| 1860 | South Carolina secedes (December 20) |
| Civil War and Reconstruction | |
| 1861-65 | American Civil War |
| 1861 | Mississippi secedes (January 9) |
| Florida secedes (January 10) | |
| Alabama secedes (January 11) | |
| Georgia secedes (January 19) | |
| Louisiana secedes (January 26) | |
| Texas secedes (February 1) | |
| Confederate States of America (February 4) | |
| Virginia secedes (April 17) | |
| Arkansas and Tennessee secede (May 6) | |
| North Carolina secedes (May 21) | |
| 1863 | West Virginia |
| 1864 | Nevada |
| 1865 | Lee surrenders to Grant at Appomattox |
| 1866 | Tennessee readmitted (July 24) |
| 1867 | Nebraska (March 1) |
| Alaska Purchase (March 11) | |
| 1868 | Arkansas readmitted (June 22) |
| Florida and Louisiana readmitted (June 25) | |
| North Carolina readmitted (July 4) | |
| South Carolina readmitted (July 9) | |
| Alabama readmitted (July 14) | |
| 1870 | Virginia readmitted (January 26) |
| Mississippi readmitted (February 23) | |
| Texas readmitted (March 30) | |
| Georgia readmitted (July 15) | |
| 1876 | Colorado |
| The Guilded Age | |
| 1889 | North Dakota and South Dakota (November 2) |
| Montana (November 8) | |
| Washington (November 11) | |
| 1890 | Idaho (July 3) |
| Wyoming (July 10) | |
| 1893 | Annexation of Hawaii |
| 1896 | Utah |
| 1898 | Spanish-American War |
| 1898 | Treaty of Paris (December 10) |
| 1898-1902 | Filipino Insurrection |
| 1898-1902 | Occupation of Cuba |
| 1902 | Annexation of Guantanamo Bay |
| 1903 | Panama U.S. Protectorate |
| 1906-08 | Intervention in Cuba |
| 1907 | Oklahoma |
| 1912 | Intervention in Honduras |
| 1912 | New Mexico (January 6) |
| Arizona (February 12) | |
| 1914 | Occupation of Veracruz |
| 1915-34 | Intervention in Haiti |
| 1916-17 | the Pershing Expedition |
| 1916-24 | Intervention in Dominican Republic |
| 1917 | Intervention in Cuba |
| 1917 | Annexation of St. John |
| 1917-18 | The Great War |
| 1919 | Intervention in Honduras |
| 1928-34 | Intervention in Nicaragua |
| 1942-45 | World War II |
| The Cold War | |
| 1950-53 | the Korean War |
| 1958 | Intervention in Lebanon |
| 1959 | Alaska (January 3) |
| Hawaii (August 21) | |
| 1961 | Bay of Pigs |
| 1965 | Intervention in Dominican Republic |
| 1965-75 | the Vietnam Conflict |
| 1983 | Invasion of Grenada |
| The "New World Order" | |
| 1991 | the Persian Gulf War |
| 1992 | Intervention in Somalia |
| 2002 | the Afghanistan War |
| 2003 | Intervention in Liberia |
| 2003-? | the Iraq War |
This timeline only includes direct military interventions and territorial acquisition. It does not include American intervention (either overt or covert) through proxies (such as in Guatemala, El Salvador, Iran, etc.). Nor does it outline the penetration of American economic and political power in various parts of the globe, the American alliance system, military aid, etc.