Treasure Island is a 404 acre (1.64 square kilometer) artificially constructed island in the middle of the San Francisco bay, attached to neighboring Yerba Buena Island by a causeway. The island was built in 1939 for the Golden Gate International Exposition, a World's Fair intended to celebrate the construction of the Bay Bridge and the heritage of the Bay Area. Like many construction projects of the 1930s, it was built by the Works Progress Administration, and was developed with an assortment of fanciful buildings, most of which have since been destroyed.
Initially, the plan for Treasure Island was to convert it to an airfield after the closure of the Exposition. To this end, several hangars were built for the Pan-American Clipper; these can still be seen on the South end of the island. However, the involvement of the United States in the Second World War brought Treasure Island to the attention of the Navy. The central location made it ideal for storing equipment and stationing troops, and the Navy offered to trade Mills Field, South of San Francisco, for Treasure Island. The agreement was made, and Treasure Island because Naval Station Treasure Island.
From 1941 to 1996, Treasure Island was an active military base. Most of the buildings from the World's Fair were torn down, although the Administration Building by the entrance was left intact. Barracks, training facilities, and recreational buildings were constructed on the island, which was closed to the public. In 1993, under Base Realignment and Closure, the navy decided to decommission Treasure Island, along with the Presidio in San Francisco. By 1997, the base had been entirely closed.
In 2000, former military housing at the North of Treasure Island was leased to a private rental agency by the navy. The housing currently supports a small population, and the center of the island houses a Job Corps training facility. The former clipper hangars are used as sound stages and film studios. Although the island is open to the public, most of the buildings are off limits because of safety issues. The island is also in the process of environmental cleanup, to remove contaminants left behind by the navy.
Plans to develop Treasure Island began to be discussed in the late 1990s, and several ideas were put forward. No development can be undertaken until the island is cleaned and turned over to the City of San Francisco. The island also requires significant seismic work, as it is subject to liquefaction during an earthquake and it is also sinking. It is estimated that no serious development work will begin on Treasure Island until 2012, and numerous roadblocks may hinder this process for even longer.