| | |
Date
| Territory | Notes |
1783
| Former 13 colonies | Treaty of Paris of 1783 following American Revolutionary War |
1803
| Louisiana Purchase | Purchased from France for $15 million, including assumed claims |
| 1819 | Florida (East and West) | Purchased from Spain for $5 million in assumed claims under Adams-Onís Treaty |
| 1845 | Texas | Annexation of independent republic |
| 1846 | Oregon Territory | The Oregon Treaty with Great Britain |
| 1848 | Mexican Cession | Purchase from Mexico following American-Mexican War; $15 million plus 3.25 million in assumed claims |
| 1853 | Gadsden Purchase | Purchased from Mexico for $10 million |
| 1857 | Baker Island
Howland Island | Unincorporated territory claimed under Guano Act of 1856; under the jurisdiction of the U.S.
Fish and Wildlife Service |
| 1857 | Navassa Island | Unincorporated territory claimed under Guano Act of 1856; under the jurisdiction of the U.S. Fish and Wildlife Service |
| 1858 | Jarvis Island | Unincorporat
|