Curious Patents
Lincoln's Patent
In 1849, a few months after his only term in Congress ended, Abraham Lincoln patented a way to lift a stranded steamboat over a sandbar with air. He is still the only American president to hold a patent.
Watch the episode
Operate the invention
This is the model from the episode, built from Lincoln's own drawings. Turn the shaft and watch the spars drive the chambers down into the river, open them like bellows and fill them with air. Drag to look around, and pinch or scroll to zoom.
Full-size figures scale this reconstruction to a 140 ft steamboat, as Ian de Silva scaled Lincoln's original model (Journal of the Abraham Lincoln Association, 2018). They are estimates from the reconstruction's proportions, which follow the patent's drawings; the patent itself gives no dimensions. De Silva's own estimate, from the chambers he measured on the surviving model, is about 15 inches of lift from 4,130 ft³ of air. Lengthen the check ropes here and you get close to it.
The parts, in Lincoln's letters
- A
- Buoyant chambers: stiff tops and bottoms, sides of india-rubber cloth, so they fold flat or open to hold air.
- B
- Boxes on the guards (the wide deck overhanging the hull) that hold the folded chambers.
- C
- The main shaft, running the length of the boat just under the upper deck, turned by the steam engine or by hand.
- D
- Spars that slide through each chamber's top and are fixed to its bottom.
- f
- Ropes wound around the shaft, running over rollers and down to the spars, tied at i.
- e
- Check ropes that catch the chamber tops, so the chambers open as their bottoms are driven down. Their length sets how deep the chambers go.
- m
- Openings in the chamber tops that let air in and out.
Read the original patent
The patent is two pages of text and one sheet of drawings. It is in the public domain. Click a page for full resolution.
Download the patent (PDF, 230 KB) · Google Patents record · Applied for 10 March 1849, granted 22 May 1849.
Sources
Every fact in the episode comes from these. Where the sources disagree, the episode says so.
The patent and the model
- A. Lincoln, Buoying Vessels over Shoals, US Patent 6,469, 22 May 1849 (PDF).
- Lincoln's patent model, Smithsonian National Museum of American History, object nmah_213141. Photographs CC0 (Smithsonian Open Access).
- Z. C. Robbins to A. Lincoln, 13 April 1849, The Papers of Abraham Lincoln.
- Patent Act of 1836, §6 (the model requirement). W. Janssen, Patent Models Index, Smithsonian Contributions to History and Technology 54 (2010).
Lincoln's life
- W. H. Herndon and J. W. Weik, Herndon's Lincoln (1889), vol. 1 and vol. 2.
- M. Burlingame, Abraham Lincoln: A Life, vol. 1 ch. 3 and ch. 8.
- The Lincoln Log (itinerary, September–October 1848).
- A. Lincoln, Second Lecture on Discoveries and Inventions (1859); Collected Works, vol. 3.
- O. Edwards, "Inventive Abe", Smithsonian, October 2006 (Paul Johnston's comments).
- USPTO, remarks of 7 May 2025: "He is the only President to have been granted a patent."
Would it work?
- I. de Silva, "Evaluating Lincoln's Patented Invention", Journal of the Abraham Lincoln Association 39:2 (2018).
- C. Goodyear, US Patent 3,633 (vulcanised rubber), 15 June 1844.
River steamboats
- J. Hall, The West: Its Commerce and Navigation (1848).
- K. Crisman, "The Last Voyage of the Steamboat Heroine, 1838", Chronicles of Oklahoma 91:3 (2013).
- G. B. Merrick, Old Times on the Upper Mississippi (1909), on sparring.
The ship camel and later ideas
- J. van der Vliet, "Een 'loflijk middel'", Ons Amsterdam (2018).
- Rijksmuseum, model of a ship camel, NG-MC-21 (c. 1780–1840; public domain).
- Nantucket Historical Association, "What were the camels?"
- US Patent 6,834,604, "Transporting a ship over shallows" (2004).
Images in the episode
- Library of Congress, Prints & Photographs and Geography & Map Divisions: the Lincoln daguerreotype (c. 1846–47, attributed to N. H. Shepherd), Alexander Gardner's 1863 portrait, the Patent Office model room, the steamboat Mayflower, Bodmer's Snags, St. Louis in 1832, and maps by E. B. Strong (1836) and J. Calvin Smith (1844).
- Fontayne & Porter, Cincinnati Panorama of 1848 (public domain, via Wikimedia Commons).
- U.S. Navy photograph of a lift bag, 2010 (public domain; no endorsement implied).