Abraham Lincoln is the only U.S. president to hold a patent.

He received Patent 6469 for “A Device for Buoying Vessels Over Shoals” in 1849.

The invention was a set of bellows, a larger version of fireplace bellows, that attached to the hull of a ship just below the water line. The idea was the bellows would be filled with air when the ship reached a shallow spot, and the air would make the ship float higher. It was never commercially produced.

A Springfield mechanic helped design the model, which Congressman Lincoln  whittled with his own hands.  A replica is on display at the Smithsonian Institution National Museum of American History. The original is too fragile to display.

Source: americanhistory.so.edu