The exact origins of the Uncle Sam caricature are unknown, but it is widely believed by historians that the inspiration came unwittingly from Samuel Wilson, a businessman from Troy, N.Y., who supplied beef to troops during the War of 1812.

Wilson was a slaughterer and meat packer who packed many barrels full of beef to ship to the troops. He labeled the barrels "U.S." to reflect sale to the government, and his workers began to joke that the initials stood for "Uncle Sam" Wilson. Those shipments with the initials led to the idea that Uncle Sam symbolized the federal government and that the troops fought on behalf of Uncle Sam.

The first known pictures of "Uncle Sam" were displayed in the 1830s. The image of a tall and lanky white-haired man with goatee did not look like Sam Wilson, the meat packer. It was the inspiration of 19th century political cartoonists, mainly Thomas Nast, who designed the earliest images of Uncle Sam in star-spangled clothes.

The most famous picture of Uncle Sam was drawn by James Montgomery Flagg and appeared on the July 6, 1916, cover of Leslie's Weekly magazine with the title, "What Are You Doing for Preparedness?" Millions of copies were reproduced between 1917 and 1918 as an Army recruiting poster with the words, "I Want You!"