Treasure Island is about 1 mile long, 2.25 miles east-northeast of North Point in San Francisco Bay. The feature is connected to Yerba Buena Island by a cause-way. The island was built from 1936 to 1938 by pumping sand and mud dredged from the bay into an enclosure formed by a rock retaining wall; it was used for Goden Gate International Exposition in 1939 and 1940, and it became a navy installation during World War II. Source: "Durham's Place-Names, San Francisco Bay Area", pg. 183. Hope this helps. Roberta