9. Johnston Atoll (Kingdom of Hawaii, disputed with Britain)
Johnston Atoll was claimed by the United States under the Guano Islands Act of 1856. In 1858, both the U.S. and the Kingdom of Hawaii laid claim to the atoll, leading to a brief dispute. The U.S. continued to assert control, and after Hawaii’s annexation in 1898, Johnston Atoll became part of the U.S. territory. The atoll was used for military and nuclear testing, and its sovereignty was assured following Hawaii’s annexation (britannica.com).
