For more than two centuries, whenever there has been a debate in the United States, political cartoons have taken part, and in some cases, pushed the debate to its limits. Political cartoons began as a street-level phenomenon. In the late eighteenth and early nineteenth centuries, they were often posted on walls or passed from person to person, as well as being published in newspapers. By the end of the nineteenth century, they were an important part of the growing popularity of newspapers and magazines, and the intense competition for readership made provocative cartoons a valuable selling point. At the beginning of the twenty-first century, political cartoons appear in a wide range of online publications and can still stir up controversy.