The Midway Islands consist of a circular atoll, 6 mi in diameter, that encloses two islands. Lying about 1,150 mi west-northwest of Hawaii, the islands were first explored by Captain N. C. Brooks on July 5, 1859, in the name of the U.S. The atoll was declared a U.S. possession in 1867, and in 1903 Theodore Roosevelt made it a naval reservation. The island was renamed “Midway” by the U.S. Navy in recognition of its geographic location on the route between California and Japan. Air traffic across the Pacific increased the island's importance in the mid-1930s; the San Francisco–Manila mail route included a regular stop on Midway. Its military importance was soon recognized, and the navy began building an air and submarine base there in 1940. The Battle of Midway, which took place from June 3–6, 1942, was considered a turning point in World War II. After the war, the strategic importance of the island declined; the Midway stop for commercial air traffic was eliminated in 1950, and the air base closed in 1992.