Uncle Sam is 100 years old. At least, that's the age of the most iconic image of that famous American symbol.

In the past century, there have been all sorts of depictions of Uncle Sam, but when the United States entered World War I in 1917, artists were enlisted to help the war effort with pen, ink and paint. That led to an Army recruiting poster that has stood the test of time.

But there's more to America's most well-known uncle. Here are five things about Uncle Sam you might not know.

1. A meat-packer inspired the name

Many historians attribute the term “Uncle Sam” to a Troy, New York, businessman, Samuel Wilson, whose friendly manner earned him the nickname “Uncle Sam” to his friends and customers. He supplied beef to the Army during the War of 1812. The beef was delivered in barrels stamped “U.S.” to indicate government property, but soldiers jocularly said it belonged to “Uncle Sam.”

Wilson, by the way, served in the American Revolution at age 15, so if he was the inspiration for the name, he had the patriotic chops for it.

2. Uncle Sam didn’t always have a beard

Early depictions in publications like Punch and the New York Lantern in the mid-19th century symbolized America as a man with striped pants, a swallow-tail coat and stovepipe hat but clean-shaven. After the Civil War, political cartoonist Thomas Nast popularized the image of Uncle Sam, eventually giving him the white beard and stars-and-stripes suit. (Nast also is responsible for creating the donkey as a Democratic Party symbol and the elephant as a Republican symbol.)

3. America’s symbol wasn’t always a man

Before Uncle Sam, there was Columbia.

Derived from Christopher Columbus, Columbia was a term used to describe North America and the United States, and was the name chosen for the district George Washington carved out for the nation’s capital. In artwork, Columbia was presented as a woman, though no particular type of dress or appearance became commonplace. Nast used Columbia in several of his editorial cartoons.

4. Uncle Sam had another competitor

Another symbol in popular culture was Brother Jonathan, which originated in England as a derogatory reference to Puritans, then to New Englanders, then to colonists in general. The name caught on and spread to editorial cartoons on both sides of the Atlantic.

5. James M. Flagg made 46 World War I recruiting posters

But everybody remembers just one Uncle Sam. For good reason. Flagg’s poster of a stern-looking Uncle Sam — red tie, blue coat and white top hat accented with a blue hatband and white stars — pointing with the words “I WANT YOU FOR THE U.S. ARMY” became the definitive image of this American symbol. He drew inspiration from a 1914 British recruiting poster by Alfred Leete depicting Lord Kitchener, the British war secretary, pointing at the viewer saying, "Your country needs YOU.”

Kitchener died during the war. Uncle Sam lives on.

Follow George Morris on Twitter, @GWMorris.