Uncle Sam, nickname and cartoon image, is used to personify the U.S. government. It is derived from the initials U.S. and was first popularized on supply containers during the War of 1812.

Uncle Sam Poster
Samuel Wilson, a businessman from New York also known as Uncle Sam, stamped his shipments during the War of 1812 with the initials of the United States, U.S. The coincidence led to the use of the nickname Uncle Sam for the United States government.
The first visual representation or caricature of an Uncle Sam figure, attired in stars and stripes, appeared in political cartoons in 1832. The character came to be seen as a shrewd Yankee. In the 20th century Uncle Sam has usually been depicted with a short beard, high hat, and tailed coat. In 1961 the U.S. Congress adopted the figure as a national symbol.
James Montgomery Flagg’s recruiting poster for World War I (1914–1918), with the beckoning words ― I WANT YOU, has become one of the best-known portrayals of the character known as Uncle Sam.