Kwajalein is one of the world's largest coral atolls as measured by area of enclosed water. Comprising 97 islands and islets, it has a land area of 16.4 km² (6.33 mi²), and surrounds one of the largest lagoons in the world, with an area of 2174 km² (839 mi²).
These are the two main islands used by the U.S. personnel, and their families are accommodated in trailers or hard housing. Most unaccompanied personnel live in apartment-style housing.
Since 1944, when American forces captured the atoll from the Japanese in the Battle of Kwajalein, it has been used for military purposes by the U.S., while escaping the fates of the nearby atolls of Bikini, Rongelap, and Enewetak—Kwajalein has never been a site for nuclear detonations and has never been covered with any significant nuclear fallout from the tests that were conducted during the 1940s and 1950s. It was, however, the main support site for this weapons-testing program, namely Operation Crossroads.