P. T. Barnum, the American Circus promoter, once said, when remarking on the importance of the clown,
"Clowns are pegs used to hang circuses on."
The American Circus Clown provided comic relief between acts and filled in when staging was being changed. His most important function was to relieve tension between the serious and often times, dangerous acts of Lion Tamers, equestrians and trapeze artists. These clowns were talking and singing comedians, who most often did pantomime in the center ring and whose primary function  was to punctuate the end or beginning of other performers acts.

Dan Rice, one of the first famous clowns in the United States, was popular during the Civil War. Abraham Lincoln was one of his greatest fans. In fact, it was widely believed that Rice's face and his characteristic costume of striped pants, long beard, and stove pipe hat, inspired the early drawings of Uncle Sam.

Circuses were small then and clowns were singers and joke tellers. As Circuses grew and audiences got bigger, performers could no longer be heard. A new kind of clowning, called Pantomime, developed and clowns began walking among the crowds, repeating their act for small groups as they mingled. It became more difficult for clowns to become famous under these circumstances.

Felix Adler, was billed as the 'King of the Clowns'. He used trained animals in his act.
Lou Jacobs drove a tiny automobile no bigger than a baby buggy. Ernie Wiswell and Buck Baker drove cars which seemed to drive themselves. Large modern circuses, usually include both, the Clown Band, the Clown Wedding and the Fire Department in their repertoire.

In European circuses, European clowns of merit include Toto (Armando Novello), Marceline, Grock, Coco (Raoul Jouin), members of the Fratellini family, and Oleg Popov.