I probably should have thought about writing this blog post last week, but it was the July 4th celebration that got me thinking about it. There are a lot of distinctly American characters that have first appeared in comic strips and have become American icons. However, there are also prominent American symbols that first appeared in comic strips as well. Two of them were clearly popularized by a particular newspaper cartoonist named Thomas Nast.
Nast was a very prolific cartoonist. He's often given credit for creating characters such as Uncle Sam and Columbia, and though he did use them in his cartoons, he didn't create them. He also didn't popularize Uncle Sam nearly as well as James Flagg did with his Army recruitment poster.
He did, however, popularize the use of the donkey as a symbol for the Democratic party as well as begin the use of the elephant as a symbol for the Republican party. The donkey had been used before, mainly to refer to Andrew Jackson. While it originally was meant to be derogatory, Jackson adopted it for use in his campaign. Nast revived it many years later and used it as a symbol of the entire Democratic party in several of his cartoons. One notable cartoon had a donkey covered in a lion skin scaring away several other animals, one of which was an elephant labelled "The Republican Vote." Both symbols were used numerous other times, and the the parties, much like Andrew Jackson, later adopted them as official party mascots.
Nast is also sometimes credited with popularizing the "modern" image of Santa Claus as a large, bearded man in a red suit, but that's debatable and is a topic for another time.
For more info on Nast himself, see the following:
Thomas Nast at the Billy Ireland Cartoon Library
For more info on the origin of the elephant and donkey symbols, see the following:
"Political Animals: Republican Elephants and Democratic Donkeys", essay from Smithsonian Magazine
The Donkey and Elephant, essay at Our White House