Self taught American inventor Oliver Evans designed an improved steam engine which used steam to push instead of pull a piston. After demonstrating the engine, he got a contract to build a steam machine for dredging Phildelphia's docks on the Schuylkill river. However, there were certain difficulties with the job. The steam engine was to be built into a scow that weighed 15.5 tons. Evan's shop was 16 miles up the river, and a mile and a half from the river. Evans decided to build the scow to drive itself the distance to the river, then to move under its own power downstream the 16 miles to the work site. Thus, is was the first self-propelled land vehicle in the U.S. (Cugnot's vehicle was earlier), one of the first steam powered boats (Fitch's paddle boat was earlier), and the first amphibian vehicle.
When finished in 1805, Evans fired up the 5 hp steam engine, drove the boat around the town square, then to the river, where he converted it to a paddle wheel boat, and steamed downriver against a headwind that had the sailboats on the river tacking back and forth. You know that a 5 hp engine driving a 15 ton vehicle was a little underpowered. That would be like powering a semi tractor with a lawn mower engine. However, it worked dredging mud for several years.
He called the dredge/auto/boat the Oructor Amphibolos, which is Latin for "Amphibious Dredge." This was the first overland vehicle in the U.S. and the first amphibian vehicle anywhere in the world.