The origin of the term Uncle Sam, though disputed, is usually associated with a businessman from Troy, N.Y., Samuel Wilson, known affectionately as “Uncle Sam” Wilson. The barrels of beef that he supplied the army during the War of 1812 were stamped “U.S.” to indicate government property. This identification is said to have led to the widespread use of the nickname Uncle Sam for the United States; and a resolution passed by Congress in 1961 recognized Wilson as the namesake of the national symbol.

Uncle Sam and his predecessor Brother Jonathan were used interchangeably to represent the United States by U.S. cartoonists from the early 1830s to 1861. Cartoonists of the British humour magazine Punch helped evolve the modern figure by their drawings of both Brother Jonathan and Uncle Sam as lean, whiskered gentlemen wearing top hats and striped pants. Probably the first U.S. political cartoonist to crystallize the figure of Uncle Sam was Thomas Nast, beginning in the early 1870s. One of the most familiar treatments in the 20th century was shown in James Montgomery Flagg's World War I recruiting poster, also used in World War II, for which the caption read, “I Want You.”