Online, teachers can find dozens of excellent sources. One great place to start is the Washington Post On Politics page, where you will find links to the work of Herblock, the editorial cartoonist at the Post since 1946. Your local newspaper may post an editorial cartoon each day. This page provides an overview of the political cartoon from Roman times through the American Revolution and the Civil War. This site is appropriate for upper middle school and high school students.
Footnotes nicely document the information offered.
The American Presidency Grolier presents this overview of political cartoons and how people have used them during the past two centuries to satirize our presidents. This site provides background information that students need to interpret editorial cartoons. This site provides a great presentation highlighting Thomas Nast's exposure of Boss Tweed and his corrupt political machine of the late 1800s. Clickable thumbnail images become enlarged cartoons. This site will help students appreciate the power editorial cartoons can have in a democracy.