New Jersey was a site of shipbuilding throughout the World War I period. Refineries and ammunition factories were also built to supply war material. Factories such as the Singer Company based in Elizabeth converted from making sewing machines to making weapon parts. Several camps and the forts were opened for soldiers during the war. The roles of these sites were generally to provide a location for soldiers to stock up on supplies, receive medical treatment, or become discharged. Several Allied ships were sunken off of the coast of New Jersey. Other factors contributing to the U.S. Entry into the war include German sabotage of both Black Tom in Jersey City, and the Kingsland Explosion in what is now Lyndhurst.