Uncle Sam (with the same initials as United States) is a common national personification of the United States, depicting the federal government or the country as a whole. Since the early 19th century, Uncle Sam has been a popular symbol of the U.S. government in American culture and a manifestation of patriotic emotion. Uncle Sam has also developed notoriety for his appearance in military propaganda, made popular in 1917 World War I recruiting poster by James Montgomery Flagg.
According to legend, the character came into use during the War of 1812 and may have been named after Samuel Wilson. The actual origin is obscure. The first reference to Uncle Sam in formal literature (as distinct from newspapers) was in the 1816 allegorical book The Adventures of Uncle Sam, in Search After His Lost Honor.