The United States military has at least 750 bases in 80 countries around the world. The largest proportion of these, of course, are in the 50 states. After this, the biggest share of American military installations are in Europe, followed by Southeast Asia, including Camp Humphreys in South Korea. While Camp Humphreys, built in 1950, is the largest U.S. military base in a foreign country, it is far from the oldest.

To determine the oldest U.S. active military bases that are overseas, 24/7 Wall St. reviewed the study, U.S. Military Bases Abroad, 1776-2021 by David Vine, professor at the department of anthropology at American University. We ranked the bases according to the year they opened, listing the 23 bases founded by 1943 at the latest. Data on the number of active-duty personnel and bases within each country as well as estimated land acreage of each base came from the Quincy Institute for Responsible Statecraft, a military think-tank.

Out of the 23 bases on the list, 13 are located in Puerto Rico, operated by the Army, Navy, and Air Force. Not surprising given the important strategic position Puerto Rico holds between the Caribbean Sea and the Atlantic Ocean. The first of these was constructed in 1902. (Also see, the six European bases where the U.S. is storing nuclear bombs.)

Puerto Rico was one of the territories the United States received in the wake of its victory over Spain in the Spanish-American War in 1898. Cuba, which gained independence from Spain following that war, agreed to lease Guantánamo Bay to the U.S. Navy on its southeastern shore in 1903. Other possessions the U.S. secured from Spain in the Pacific – Guam and Wake Island – have military bases.

Elsewhere, four of the oldest U.S. overseas bases are in the United Kingdom, established there just after America entered the war in 1941. That same year, the U.S. began leasing from Denmark the Thule Air Base in Greenland, which at more than 233,000 acres, is by far the largest overseas military base by physical size. (This is the largest military base in each state.)

Click here to see the oldest international military bases.