In addition to the naval shipyard, other military functions were established on the island. From 1857 to 1975 the Naval Ammunition Depot at the southern tip of the island manufactured, tested, and stored ammunition that supplied the Navy's Pacific operations. As the Navy's presence in the Pacific grew, the depot required greater storage capacity. The Western Magazine was built in the 1930s on the island's remote western shore, a safe distance from the ammunition manufacturing area. Although the ammunition was removed long ago, dozens of magazines still stand. These massive structures have thick reinforced concrete walls and lightweight roofs, designed to withstand the blast of an accidental explosion by sending most of the explosive force up through the roof, reducing damage to nearby structures and lowering the risk of injury to workers.