There's always been some question as to the origin of Uncle Sam and who he is named after (if anyone).
The most popular theory is that everybody's Uncle Sam was based on Samuel Wilson. Wilson was born in 1766 and as a young man he and his brother walked there way to Troy, New York.
Wilson was a butcher by trade and during the War of 1812 he provided the U.S. Army with large shipments of meat. The story has it that the meat was sent in large barrels with the initials U.S. stamped on it.
The story goes on to say that someone who saw this jokingly referred to it as a delivery from Uncle Sam Wilson (US Wilson). This immediately caught on, it is said, and Uncle Sam and the U.S. government became one in the same.
The symbol of Uncle Sam took on a likeness nothing at all like that of Samuel Wilson. Uncle Sam was portrayed as a tall, slim figure with white whiskers, wearing a top hat, star-spangled swallowtail coat, and striped pants.
This was the product of the imagination of political cartoonists. A prominent 19th-century political cartoonist, Thomas Nast, produced many of the earliest cartoons of Uncle Sam.
In the cartoons Uncle Sam was often confused with Yankee Doodle (or Brother Jonathan). Both figures wear star-spangled suits of red, white and blue.
However, Brother Jonathan was usually drawn with a feather in his cap, while Uncle Sam was not; and Uncle Sam is nearly always drawn with a beard, while Brother Jonathan was clean-shaven.
The poster was painted by James Montgomery Flagg in 1916-1917.