'Uncle Sam' is today a symbolic name standing for the United States. Historians assume that the expression was coined during the war in 1812. Businessman Samual Wilson from Troy in New York State shipped boxes with canned meat to the troops and on the boxes the initials U.S. respective US could be found. Meant to be as the approval stamp for shipment. Workers of Wilson stated or joked that it would stand for 'Uncle Sam', how they nicknamed Samual Wilson. The troops, of course, initially associated the initials 'U.S.' with United States, because the meat was property of the United States. From the day on when it made the round - may be the workers of Sam Wilson who became soldiers spread the word - that U.S. could or would stand for 'Uncle Sam'... the nickname for the United States of America was established. Property of the U.S. Government was from there on 'property of Uncle Sam', 'a.k.a.' United States Government.
The most famous illustration of Uncle Sam is the Recruiting Poster of 1917 by James Montgomery Flagg (1877-1960), who stated once that he stood his own model, because he wanted to save money for a hired model. The Poster was used during World War I and later in WW II, too.
Different interpretations of the original 'Uncle Sam' look were created over the centuries by artists and cartoonists like Thomas Nast
Eventually, in 1961, Congress passed a resolution that recognized Samuel Wilson as the inspiration for the symbol Uncle Sam. It was John F. Kennedy who signed the bill.
'Uncle' Sam Wilson was born in Menotomy, which is today Arlington, MA., on September 13, 1766. He lived from 1789 until he died on July 31, 1854, in Troy, New York. His grave is on the Oakwood cemetery in Troy.
Uncle Sam, Recruiting Poster, 1917