In 1752, the American colonies stood on the brink of war with France. As English-speaking settlers moved inland, they were constantly bumping against French territory (France, in the mid-18th century laid claim to a portion of the American interior stretching from New Orleans, up through the American Midwest into what is now Eastern Canada).
Franklin owned the Pennsylvania Gazette at the time, and believed that a defensive union of the colonies was essential to protect against possible French attacks. In a published drawing entitled "Join, or die," Franklin depicted a snake cut into eight pieces: One piece for each of the colonies. The engraving referenced a popular superstition at the time that if the pieces of a decapitated snake were arranged together before sunset, the snake would come back to life.
It's no Doonesbury, but "Join, or die" is widely believed to be America's first political cartoon. The simple drawing was reproduced throughout the American colonies, and even staged a comeback during the American Revolution. Meanwhile, other publishers took Franklin's lead and began using graphics and snippets of text to communicate their own political ideals. Franklin had unwittingly kicked off a new American art form, and today, more than 300 editorial cartoons are published daily in American newspapers.