Short answers, pulled from the story.
The figure appeared in print as early as 1816 within an allegorical book titled The Adventures of Uncle Sam, in Search After His Lost Honor. An 1810 edition of Niles' Weekly Register defined Uncle Sam as a cant term in the army for the United States.
Samuel Wilson was a meatpacker from Arlington, Massachusetts who moved to Troy, New York to supply rations for soldiers during the War of 1812. Contractors were required to stamp their names and origins onto food packages sent to troops, and Wilson's barrels bore the letters E.A. followed by U.S., which stood for United States.
James Montgomery Flagg created a standard appearance during World War I that eventually adopted the white top hat with stars, blue tail coat, and red-and-white-striped trousers that define him today. This visual identity replaced the earlier interchangeable use of names and styles that had existed since the early 1800s.
The image first appeared publicly on the cover of Leslie's Weekly magazine on the 6th of July 1916. More than four million copies of this specific image were printed between 1917 and 1918 to recruit soldiers into the US Army.
A Congressional joint resolution designated the 13th of September 1989 as Uncle Sam Day to commemorate Wilson's birthday. Samuel Wilson died on the 31st of July 1854 at age 87 and is buried in Oakwood Cemetery in Troy.