In 1959, Lockheed Aircraft Company purchased the Puget Sound Bridge and Dredging Company of Seattle, Washington, which was founded in 1898.  The 18-acre shipyard was located on the west side of Harbor Island and operated from the 1930s to 1987.  Lockheed’s shipbuilding projects included several ferries for the Alaska Marine Highway in the 1960s, several Knox class frigates for the U.S. Navy in the late 1960s and early 1970s, seven landing platform dockships (LPDs) of the Cleveland and Trenton classes for the U.S. Navy, two Polar class icebreakers for the U.S. Coast Guard in the 1970s, and more.  Lockheed won the largest shipbuilding contract in its history in 1974 when the U.S. Navy ordered two submarine tenders to support the Los Angeles class nuclear submarines.