Uncle Sam (initials U.S.) is a common national personification of the American government that, according to legend, came into use during the War of 1812 and was supposedly named for Samuel Wilson. The first use of Uncle Sam in literature was in the 1816 allegorical book "The Adventures of Uncle Sam in Search After His Lost Honor" by Frederick  Augustus Fidfaddy, Esq. An Uncle Sam is mentioned as early as 1775, in the original "Yankee Doodle" lyrics of the Revolutionary War. It is not clear whether this reference is to Uncle Sam as a metaphor for the United States. The lyrics as a whole clearly deride the military efforts of the young nation, besieging the British at Boston. The 13th stanza is:

Old Uncle Sam come there to change Some pancakes and some onions, For ’lasses cakes, to carry home To give his wife and young ones.    

Before Uncle Sam

The earliest known personification of what would become the United States was "Columbia" who first appeared in 1738 and sometimes was associated with Liberty.

Columbia

With the American Revolutionary War came "Brother Jonathan" as another personification and finally after the War of 1812 Uncle Sam appeared.

The evolution of Uncle Sam

The term Uncle Sam is reputedly derived from a Samuel Wilson, a meat packer from Troy, New York, who supplied rations for the soldiers. There was a requirement at the time for contractors to stamp onto the food they were sending their name and where the rations came from. Wilson's packages were labeled “E.A – US.” When someone asked what that stood for, a coworker joked and said “Elbert Anderson (the contractor) and Uncle Sam,” referring to Sam Wilson, though it actually stood for United States.

As early as 1835 Brother Jonathan made a reference to Uncle Sam implying that they symbolized different things: Brother Jonathan was the country itself while Uncle Sam was the government and its power.

By the 1850s the name Brother Jonathan and Uncle Sam were being used nearly interchangeably to the point that images of what had been called "Brother Jonathan" were now being called Uncle Sam. Similarly, appearance of both personifications varied wildly. For example, one depiction of Uncle Sam in 1860 depicted him looking like Benjamin Franklin, (an appearance echoed in Harper's Weekly's June 3, 1865 "Checkmate" political cartoon) while the depiction of Brother Jonathan on page 32 of the January 11, 1862 edition Harper's Weekly looks more like the modern version of Uncle Sam (except for the lack of a goatee).

However, even with the effective abandonment of Brother Jonathan (i.e. Johnny Reb) near the end of the Civil War, Uncle Sam didn't get a standard appearance until the well-known "recruitment" image of Uncle Sam was created by James Montgomery Flagg (inspired by a British recruitment poster showing Lord Kitchener in a similar pose). It was this image more than any other that set the appearance of Uncle Sam as the elderly man with white hair and a goatee wearing a white top hat with white stars on a blue band, and red and white striped trousers.

The image of Uncle Sam was shown publicly for the first time, according to some, in a picture by Flagg on the cover of the magazine Leslie's Weekly, on July 6, 1916, with the caption "What Are You Doing for Preparedness?" More than four million copies of this image were printed between 1917 and 1918.

While Columbia had appeared with either Brother Jonathan or Uncle Sam her use as personification for the USA had declined in favor of liberty and once she became the mascot of Columbia Pictures in the 1920s she was effectively abandoned.

Flagg's image also was used extensively during World War II during which the U.S. was codenamed 'Samland' by the German intelligence agency Abwehr. The term was central in the song The Yankee Doodle Boy which in 1942 featured in the musical Yankee Doodle Dandy.

There are two memorials to Uncle Sam, both of which commemorate the life of Samuel Wilson: the Uncle Sam Memorial Statue in Arlington, Massachusetts, his birthplace; and a memorial near his long-term residence in Riverfront Park, Troy, New York.