Abraham Lincoln’s patent number for his boat-lifting device was 6,469.
Lincoln’s invention, titled “Buoying Vessels Over Shoals,” was designed to help boats pass over shallow areas and other river obstructions. It used expandable air chambers or bellows attached to a boat’s sides; when inflated, they were intended to raise the hull enough to clear the obstruction.
Lincoln filed the application on March 10, 1849, while serving as a congressman, and the patent was issued on May 22 of that year. His idea grew from experiences on flatboats, including incidents in which boats became stuck on river shoals. The device was never put into practical production, and experts later questioned whether its mechanism would have worked effectively.
Lincoln remains the only U.S. president to receive a patent. His original patent model was rediscovered in 1997 and is held by the Smithsonian Institution.