The first recognizably modern circus, with its defining combination of horse trick riding, juggling, clowning, and acrobatics, was born in London in 1768 under the direction of an excavalryman, Philip Astley. The circus traveled rapidly, however, to the United States through the figure of John Bill Ricketts, a Scotsman who had worked primarily with Astley's rival, Charles Hughes. By the time Ricketts set up his first American shows in 1792 in New York and Philadelphia, the circus had organized various disparate but long-standing forms of popular street and fairground entertainment into a distinctive theatrical genre. The founding act for the circus was equestrian trick riding, and indeed the parameters of the circus ring itself have always been set at forty-two feet in diameter because Hughes had found this to be the optimum size within which enough centrifugal force could be generated to keep a rider in the saddle.
Before Ricketts, John Sharp in Boston and New York (1771) and Jacob Bates in Philadelphia (1772) had both pioneered equestrian displays. Yet the rapid development from this to circus was initially hamstrung in the United States during the Revolutionary years, the Continental Congress having put an injunction on all manner of public shows. Once this ban was revoked (after the Revolution), however, Ricketts's performance—a series of burlesque acts and horse-riding stunts—laid the grounds for a form of circus that, though it may have begun with a European template, was to develop in new and distinctly American ways. As though to seal the importance of the form to the developing nation, President George Washington, an enthusiastic horseman, attended Ricketts's wooden amphitheater in Philadelphia on 22 April 1793.
In the early nineteenth century, the American circus developed its most distinctive form: the tented traveling show. Where European circuses had mainly moved between limited numbers of fixed wooden amphitheaters, in 1825 J. Purdy Brown of Delaware was the first of many circus entrepreneurs to see the economic advantage of transporting the circus by horse and wagon and setting up tents in many more small and far-flung rural locations than had previously had access to a circus. Therefore, the "rolling" circus, though frequently based in Somers, New York, can be seen as a response to and an outgrowth of the dispersed and itinerant American nation in its early years. In the same period, the traveling menagerie also became integrated into the sense of what a circus was. Although Captain Jacob Crowninshield had brought a Bengali elephant to display in New York on 12 April 1796, it was Hackaliah Bailey who invented the concept of the animal as star performer. He named his African elephant Old Bet and displayed her from town to town between 1815 and her death (by gunshot) in 1816. The fact that Bailey was an early inspiration for P. T. Barnum and that Old Bet was the first star of the tented shows of Bailey's partner, Nathan Hewes, demonstrates her centrality to a preeminent American entertainment, shaped during this period.