The 16th Coast Artillery Regiment was a Coast Artillery regiment in the United States Army, along with the 15th Coast Artillery, it manned the Harbor Defenses of Honolulu and other fortified sites on Oahu, Hawaii from 1924 until broken up into battalions in August 1944 as part of an Army-wide reorganization. The regiment manned many gun batteries at locations all over Oahu. Most of the forts where they were assigned were originally built 1899–1910, and had been in caretaker status for more than 30 years. On the morning of 7 December 1941, the soldiers of the 16th Coast Artillery manned their anti-aircraft guns, bringing down six of the attacking Japanese aircraft.