The U.S. has held more possessions (outside of the contiguous U.S.) than most people realize. I couldn't find a single convenient listing of territories, so I did a bit of research and put this together. While it's not complete, it is fairly extensive. I've tried to find two sources for everything I've added, but there still may be a few errors.
| Claimed | Until | Name | Notes | Present Status |
|---|---|---|---|---|
| 1821 | 1847 | Liberia | The Society for the Colonization of Free People of Color of America | independent |
| 1822? | 1983 | Cook Islands (Manahiki, Penrhyn, Pukapuka, Rakahanga) | Guano Islands Act? | recognized as part of the Cook Islands, Cook Islands-U.S. Maritime Boundary Treaty |
| 1856 | 1981 | Serrana Bank | Guano Islands Act, U.S. Miscellaneous Caribbean Islands | ceded to Colombia |
| 1856 | 1981 | Roncador Bank | Guano Islands Act, U.S. Miscellaneous Caribbean Islands | ceded to Colombia |
| 1856? | 1897 | Clipperton Island | Guano Island Act, also claimed by France and Mexico | U.S. denounced annexation, France |
| 1856 | 1983 | Gilbert Islands (Butaritari, Makin) | Guano Islands Act | ceded to Kiribati, Treaty of Tarawa |
| 1856 | 1983 | Phoenix Islands (Birnie, Enderbury, Manra, McKean, Nikumaroro, Orona, Rawaki) | Guano Islands Act, shared with the U.K. | all except Baker and Howland ceded to Kiribati |
| 1856 | 1983 | Line Islands (Caroline, Flint, Kiritimati, Malden, Starbuck, Tabuaeran, Teraina, Vostok) | Guano Islands Act | all except Kingman Reef, Palmyra Atoll, and Jarvis Island ceded to Kiribati, Treaty of Tarawa |
| 1856 | 1983 | Funafuti, Nukufetau, Nukulaelae, Niulakita | Guano Islands Act | ceded to Tuvalu, Tuvalu-US Treaty |
| 1856 | 1983 | Tokelau (Atafu, Fakaofo, Nukunono) | no official claim? | recognized as part of Tokelau (NZ), Treaty of Tokehega |
| 1856 | present | Swains Island | received title from U.K.? | administered as part of American Samoa, Treaty of Tokehega, disputed Tokelau (NZ) |
| 1856-1857 | present | Baker Island | Guano Islands Act | unincorporated unorganized territory, U.S. Minor Outlying Islands, uninhabited |
| 1856-1857 | present | Jarvis Island | Guano Islands Act, annexed by U.K. 1889-1935, annexed by U.S. 1936 | unincorporated unorganized territory, U.S. Minor Outlying Islands, uninhabited |
| 1857 | present | Navassa Island | Guano Islands Act, U.S. Miscellaneous Caribbean Islands | unincorporated unorganized territory, U.S. Minor Outlying Islands, unihabited, disputed Haiti and others |
| 1857 | 1980 | Isla de Aves | Guano Islands Act, also claimed by Netherlands and Venezuela | Venezuela, U.S.-Venezuela Maritime Boundary Treaty |
| 1857-1858 | present | Howland Island | Guano Islands Act | unincorporated unorganized territory, U.S. Minor Outlying Islands, unihabited |
| 1858 | present | Johnston Atoll | Guano Islands Act, disputed Hawai'i | unincorporated unorganized territory, U.S. Minor Outlying Islands, used by DoD until 2004 |
| 1859 | present | Palmyra Atoll | invalidly? claimed under Guano Islands Act, annexed by U.K. 1889-1912, acquired via Newlands Resolution in 1898 | incorporated unorganized territory, U.S. Minor Outlying Islands, unihabited except researchers |
| 1859 | present | French Frigate Shoals | Guano Islands Act, leased to Hawai'i, acquired via Newlands Resolution in 1898 | part of Hawai'i (US) |
| 1860 | present? | Alto Velo Island | Guano Islands Act | administered by Dominican Republic, U.S. never renounced its claim |
| 1863 | 1972 | Swan Islands | Guano Islands Act, U.S. Miscellaneous Caribbean Islands | ceded to Honduras |
| 1867 | 1902 | Ducie Island | Guano Islands Act | annexed by U.K. as part of Pitcairn Islands |
| c. 1859-1867 | present | Midway Atoll (Midway Islands) | Guano Islands Act | unincorporated unorganized territory, U.S. Minor Outlying Islands |
| 1867 | present | Alaska | purchased from Russia | U.S. state |
| 1869 | 1981 | Quita Sueño Bank | Guano Islands Act, U.S. Miscellaneous Caribbean Islands | ceded to Colombia |
| 1869 | present | Bajo Nuevo Bank (Petrel Islands) | Guano Islands Act, U.S. Miscellaneous Caribbean Islands | unincorporated unorganized territory, unihabited, disputed Colombia, Honduras, Jamaica, Nicaragua |
| 1876 | 1877 | Lacapede Islands | Guano Islands Act, also claimed by Australia | U.S. President Grant repudiated annexation |
| 1879 | present | Serranilla Bank | Guano Islands Act, U.S. Miscellaneous Caribbean Islands | unincorporated unorganized territory, unihabited, disputed Colombia, Honduras, Jamaica, Nicaragua |
| 1893 | 1915? | Îles du Connétable | Guano Islands Act | French Guiana (Fr) |
| 1898 | present | Hawai'i | Newlands Resolution | U.S. state |
| 1898 | present? | Sikaiana (Stewart Islands) | asserted that islanders had ceded to King Kamehameha IV in 1856 | Solomon Islands (de facto), disputed |
| 1898 | 1902 | Cuba | Spanish-American War, Treaty of Paris | independent, except U.S. Guantánamo Bay Naval Base |
| 1898 | 1946 | Philippines | Spanish-American War, Treaty of Paris | independent |
| 1898 | present | Guam | Spanish-American War, Treaty of Paris | unicorporated organized territory |
| 1898 | present | Puerto Rico | Spanish-American War, Treaty of Paris | unicorporated organized commonwealth |
| 1899 | present | American Samoa | Tripartite Convention with the U.K. and Germany/Prussia, Tutuila 1900/Manu'a 1904 | unincorporated unorganized but self-governing territory |
| 1898-1899 | present | Wake Island (Wake Atoll) | claimed during Spanish-American War | unincorporated unorganized territory, U.S. Minor Outlying Islands, disputed Marshall Islands |
| 1903 | 1979 | Panama Canal Zone | Hay-Bunau Varilla Treaty | ceded to Panama, Torrijos–Carter Treaties |
| 1906 | 1977 | Rio Rico | south of the Rio Grande after the river was diverted | ceded to Mexico |
| 1914 | 1971 | Corn Islands | Bryan-Chamorro Treaty, leased from Nicaragua, U.S. Miscellaneous Caribbean Islands | returned to Nicaragua |
| 1917 | present | U.S. Virgin Islands | purchased from Denmark | unincorporated organized territory |
| 1922 | present | Kingman Reef | invalidly? claimed under Guano Islands Act 1860 | unincorporated unorganized territory, U.S. Minor Outlying Islands, unihabited |
| 1944 | 1986 | Federated States of Micronesia | WWII, part of the Trust Territory of the Pacific Islands 1947-1979 | independent, associated state |
| 1944 | 1986 | Marshall Islands | WWII, TTPI 1947-1979 | independent, associated state |
| 1944 | 1994 | Palau | WWII, TTPI 1947-1981 | independent, associated state |
| 1944 | present | Northern Marianas Islands | WWII, TTPI 1947-1978 | unincorporated organized commonwealth |
| 1945 | 1968 | Bonin Islands (Ogasawara Islands) | WWII, Treaty of San Francisco in 1952, U.S. claims as early as 1830 | returned to Japan |
| 1945 | 1972 | Ryukyu Islands (Nansei Islands) including Okinawa | WWII, Treaty of San Francisco in 1952 | returned to Japan |
| 1952 | 1968 | Minami Torishima (Marcus Island) | WWII, Treaty of San Francisco, U.S. claims as early as 1889 | returned to Japan |
Sources: