As a young man, Abraham Lincoln took a boatload of merchandise down the Mississippi River from New Salem to New Orleans. At one point the boat slid onto a dam and was set free only after heroic efforts. In later years, while traveling on the Great Lakes, Lincoln’s ship ran a foul of a sandbar. These two similar experiences led him to conceive his invention. Abraham Lincoln received Patent #6,469 for "A Device for Buoying Vessels Over Shoals" on May 22, 1849.