Roebling amphibian tractor Early Trials

Developed and, in part, financed by its inventor, Donald Roebling, the Alligator amphibian tractor is the predecessor of every Landing Vehicle Tracked (LVT) in the world. The story of the Roebling amphibian tractor starts with the devastating hurricanes which struck southern Florida in 1926, 1928, and 1932. Donald Roebling's father, financier John A. Roebling, had witnessed the loss of life brought about by these storms in the swampy areas of the Okeechobee region. Spurred by a challenge from his father to use his engineering talents to design and develop a vehicle "that would bridge the gap between where a boat is grounded and a car is flooded out," Donald Roebling, the grandson of the designer and builder of the Brooklyn Bridge, started work on his Alligator amphibian tractor in early 1933.

http://www.ibiblio.org/hyperwar/USN/ships/LVT/LVT.html