Abraham Lincoln is the only president to have been issued a patent. It started when he was a young man working on the Great Lakes and Ohio and Mississippi rivers. He was able to save a barge he was working on from sinking and presumably came up with his idea of an inflatable flotation bladder that can help lift a stranded boat.
His patent (US6,469) issued on May 22, 1849, states “a new and improved manner of combining adjustable buoyant air chambers with a steam boat or other vessel for the purpose of enabling their draught of water to be readily lessened to enable them to pass over bars, or through shallow water, without discharging their cargoes.” As a lawyer before he became president, he practiced patent and infringement law. Abraham Lincoln is quoted, “The Patent System…added the fuel of interest to the fire of genius…” testifying to his strong sense of law and human ingenuity.
Sources: Emerson, Jason (2009). Lincoln the Inventor.; Goldsmith, Harry (January 1938). “Abraham Lincoln, Inventions and Patents”. Journal of the Patent Office Society.; Edwards, Owen (October 2006). “Inventive Abe:…”.; Illinois State Library: Abraham Lincoln, Second Lecture on Discoveries and Inventions”.