The "Alligator" amphibian tractor is the progenitor of all amphibian assault vehicles used since 1941, a pioneer venture both in its design and the materials used in its construction. Donald Roebling, a grandson of Colonel Washington Roebling (designer of the Brooklyn Bridge), built an amphibian tractor to rescue victims of Florida's devastating hurricanes (particularly those in 1926, 1928, and 1932 that hit southern Florida). Nicknamed the "Alligator," the aluminum tractor was being marketed as a vehicle for oil exploration when it came to the attention of the United States Marine Corps, which was searching for a vehicle that could cross the coral reefs encircling many of the Pacific Islands. It was modified for use as a ship-to-shore transport for people and supplies during World War II. The paddle-tread propulsion system (patented in 1939) made it a true amphibian, the predecessor of all tracked landing vehicles. This example is believed to be "Alligator Three," prototype of over 15,000 various types and models. After the war, development of the helicopter precluded further civilian applications. This vehicle, which is on exhibit in the Marine Corps Air-Ground Museum at Quantico, originally was powered by a 95-horsepower Mercury engine. After World War II, this power plant was replaced with a 1952 Pontiac Silver Streak 102- horsepower 6-cylinder engine. This last engine was restored by a summer college intern working in the Marine Corps Museum's restoration shops in 1989 and placed on exhibit alongside the tractor. Its treads also are a postwar improvement and were mounted on the tractor by Roebling in 1946 or 1947. The Alligator 3 had been displayed outdoors at the Marine Corps Reserve Center in Tampa, Florida, since the mid-1960s. It was shipped to the Marine Corps Air-Ground Museum in 1984 and was completely restored by the museum staff before being placed on exhibit.