The first overseas acquisition of the United States was not Hawai’i but Midway, discovered by a commercial seaman in 1859 and claimed under the Guano Act of 1856, which said,

Whenever any citizen of the United States discovers a deposit of guano on any island, rock, or key, not within the lawful jurisdiction of any other government…and takes peaceable possession thereof, and occupies the same, such island, rock, or key may, at the discretion of the President, be considered as appertaining to the United States.

"It is exceedingly gratifying to me to have been…concerned in taking possession of the first island ever added to the dominion of the United States beyond our own shores, and I sincerely hope that this will by no means be the last of our insular annexations," wrote the captain of the US naval vessel, formalizing the acquisition in 1859. How and when Midway officially became part of Hawai’i is hard to trace, but it is now part of the string of reefs and atolls making up the 140,000-square-mile Northwestern Hawaiian Islands National Monument, established by President George W. Bush in 2006.