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The Mare Island Naval Shipyard (MINSY) was the first United States Navy base established on the Pacific Ocean. It is located 25 miles (40 km) northeast of San Francisco in Vallejo, California. The Napa River goes through the Mare Island Strait and separates the peninsula shipyard (Mare Island, California) from the main portion of the city of Vallejo. MINSY made a name for itself as the premier U.S. West Coast submarine port as well as serving as the controlling force in San Francisco Bay Area shipbuilding efforts during World War II.The base closed in 1996 and has gone through several redevelopment phases. It was registered as a California Historical Landmark in 1960, and parts of it were declared a National Historic Landmark District in 1975.