The company was developed by Sun Oil Company, and launched its first ship in 1917, just as the United States was entering World War I. By the 1920s, it had become a large shipyard that built tankers for the Standard Oil Company. At the start of World War II, it was among the country's five largest shipyards, with eight slipways. Twenty slipways were added during the war, making Sun Ship the country's biggest shipyard. At its peak, the company employed more than 40,000 workers at four shipyards, including one manned almost entirely by African Americans.