Here’s a few more details on the cranes at the Marine Terminal Park. According to the National Register of Historic Places nomination form, the cranes were originally 15 ton oil burning, steam powered locomotive gantry cranes built by McMyler Interstate Company of Cleveland, Ohio in 1917. Twenty-eight of them were purchased by the new Hog Island shipyard in 1917. There is an excellent summary of Hog Island by John Lawrence on the also-excellent Encyclopedia of Greater Philadelphia
The steam gantry cranes have a 15 ton capacity at 15 ft. radius, mounted on tracks, with holding and closing lines and clam shell buckets of 3/4 and 1 1/2 yard capacity. Provision is made for magnets at 35 ft. radius with portable electric power. In 1952 they were overhauled and the boilers replaced. They stand on four legs, and are approximately 40 ft. tall.
The first thing to realize is that the Hog Island cranes are no longer on Hog Island. When the United States entered World War I in 1917, a massive shipyard was set up alongside the Delaware River on Hog Island in Philadelphia to build transport and cargo ships, although none of the ships were completed before the war ended in 1918.
In 1930, Philadelphia bought Hog Island and transformed it into what is now the Philadelphia International Airport. Two of the cranes were sold and moved upriver to Trenton. At the Trenton Marine Terminal, they were used to load and unload ships for several decades before being taken out of service. Only the two gantries remain; the cranes that sat on top of them are gone. The Hog Island cranes were listed on the National Register of Historic Places in 1980.