Uncle Sam Day is observed on September 13, 2018. 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, who supplied rations for the soldiers. His birthday is September 13, 1766.
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.
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. He is buried in Oakwood Cemetery, Troy, New York. (With material from: Wikipedia)