At two o’clock on a November day in 1848, Congressman Abraham Lincoln walked down from his second-floor law office to the main square in Springfield, Illinois, an 18-inch model of a flatboat under his arm. With the help of a local mechanic, he had built and modified the boat to include large air chambers on each side. He had been working for weeks on this rather original “device to buoy vessels over shoals,” and was now prepared to demonstrate it to a few local townsmen in a large horse trough on the street corner.

One witness later remembered, “He then proceeded to put his model boat afloat in the water and placing a few bricks upon it until it sank to the first deck, he then applied the air pumps modeled like the old fire bellows, four in number, two on each side that were beneath the lower or first deck and in a few moments it slowly rose above the water about six inches, Lincoln remarking that each inch represented a foot, on a good sized steam boat.” The crowd listened to Lincoln’s exposition, gave three cheers and dispersed, “much impressed but not fully convinced.”

That final statement well sums up posterity’s judgment of Abraham Lincoln’s contribution to the problem of navigating rivers 160 years ago. Lincoln was the only president to hold a patent (Washington and Jefferson also were inventors, but they never patented their ideas), and yet his acute inventiveness and mechanical inclinations have long been ignored. This genius influenced his entire life—from his education and his legal practice to his visions of policy. To understand Lincoln the inventor is to better understand Lincoln the man.

In the autumn of 1847, Lincoln, then the only congressman from Illinois, was traveling by steamboat along the Great Lakes from Buffalo to Chicago, having just finished a sequence of political speeches across New England in support of Gen. Zachary Taylor’s 1848 presidential candidacy. As his ship, the Globe , passed up the Detroit River during the final days of September, it came upon another steamboat, the Canada , which had run aground. From the Globe’s deck, Lincoln watched as the Canada’s captain ordered his crew to collect all the empty barrels, boxes, and loose planks aboard the ship and force them under the sides to buoy her over the shallows. An experienced boatman of intensely curious and mechanically inclined intellect, Lincoln watched the procedure with great interest.

Grounding on sand bars and other river impediments was a common threat to shallow-water navigation in those days, as Lincoln knew well; as a young man he had spent a number of years as a riverboat hand and captain, traversing the Mississippi, Missouri, and Ohio rivers. He himself had suffered a similar predicament in 1831, when a flatboat he was crewing on the Sangamon River—loaded with hogs and barrels of bacon, pork, and corn—went aground on the Rutledge milldam below the town of New Salem, Illinois. With the bow hanging out over the dam and the stern leaking badly, he strained every nerve to pry his craft over the dam. He directed the crew to unload the hogs onto a borrowed boat while he ran into the village and borrowed an augur from the cooper shop. He then bored a hole in the bow as it stuck out into space. The cargo barrels were rolled forward, which tilted and drained the boat, enabling it to float free.

Lincoln’s experience on the Globe probably reminded him of his New Salem adventure, and for the rest of his trip home he considered solutions to this common difficulty. He settled on the idea of using inflatable chambers—similar to a giant bellows — attached to each side of a steamboat’s hull (or that of any other vessel) just below the waterline, with a system of sliding spars or shafts, ropes, and pulleys to expand the chambers with air. The main shaft would run longitudinally down the center of the boat, connected by ropes to numerous vertical shafts placed in apertures along the tops of both inflatable chambers. Turning the main shaft one way would distend the chambers, while turning it the opposite way would deflate them. When completely deflated, the chambers would contract to be stored in housing boxes secured to the vessel’s lower guard. The chambers could be inflated—either by steam power or manpower—whenever needed to buoy the ship over obstructions, without having to discharge the ship’s cargo. In Lincoln’s vision, the bellows could be inflated either simultaneously or individually.

The congressman spent eight weeks drafting a description of his idea and making a model of his design. His law partner, William Herndon, remembered Lincoln working on the model in the office, describing while he whittled the spars “the revolution it was destined to work” in steamboat navigation. (In 1865 a reporter for the Boston Globe described Lincoln’s finished model as “carved as one might imagine a retired rail-splitter would whittle,” and possessing “the air of having been whittled with a knife out of a shingle and a cigar box.”)

Lincoln’s ambitions for this “revolutionary” device were not as surprising as they might seem, for he had been mechanically minded his entire life. His father was a carpenter, mechanic, and farmer, and from age four to 21 Lincoln toiled alongside him. His years on the farm and in the wilderness turned him into a handy man: one of Lincoln’s professional associates later asserted that he “had a great deal of Mechanical genius,” easily grasping why and how machines worked. He was fascinated by science and technology, stopping to examine every new machine that he encountered. His reading choices also showed a scientific and mechanical penchant, often focusing on mathematics, geology, and astronomy. As a young man he had taught himself the art of surveying, as well as the law, and in later life he “nearly mastered” Euclidean geometry. As a politician, he was committed to the national policy of “internal improvements” for roads, bridges, and waterways.

When Lincoln left Springfield to return to Washington for the next congressional session in late November 1848, he took his model with him, retained an attorney, and applied for a patent on his device for “Buoying Vessels Over Shoals” at the U.S. Patent Office on March 10, 1849. In April this was approved, being issued on May 22, 1849, as Patent No. 6,469. It appears, however, that after all his work, Lincoln did nothing to publicize or market the invention.

His collected writings, in fact, show no evidence that he ever thought about it again. Patent Office historian Harry Goldsmith has observed that the creation “just became another one among those thousands of patents which fail of commercial success.” Historian Mark E. Neely has suggested that it went nowhere “probably because the weight of the apparatus would cause the problem he was trying to solve,” burdening the boats more than it buoyed them. Whatever the explanation, more than one historian has surmised that Lincoln’s invention may have furthered modern technology more than critics realize; the ideas behind his buoyant chambers actually may have advanced modern ship salvaging and submarine construction.

Whatever became of his own patent in 1849, Lincoln’s admiration for and wonder at discoveries and inventions never abated. While a congressman, he helped at least two of his constituents to apply for their own patents. As a lawyer, he took on at least five patent cases, and between 1858 and 1859 he prepared a lecture on “Discoveries and Inventions” that he delivered six times around the Midwest. As president, Lincoln fostered invention—he signed the bill creating the National Academy of Sciences in 1863 —and was always eager to hear of new ideas by inventors.

Today, Lincoln’s original patent model is on display at the Smithsonian Institution, while the most famous declaration in his “Discoveries and Inventions” lecture is engraved above the doors of the U.S. Patent and Trademark Office: “The patent system adds the fuel of interest to the fire of genius.” CP