Kahoolawe was used as a gunfire and bombing target by the United States military during World War II. It was a defense training area by the United States Navy from around 1941 until May 1994. Popular opinion in the state against this practice brought the end to this use. Navy has since been trying to cleanup unexploded ordnance (bombs and explosive shells) from the island. Ordnance is still buried or lying on the ground. Other items have washed down gullies and still other unexploded ordnance is underwater offshore. In 1981, the entire island was included on the National Register of Historic Places.