In 1829, at the age of 19, Barnum married 21-year-old Charity Hallett. The couple had four daughters from this marriage. In 1834 Barnum moved to New York City, where he found his vocation as a showman one year later. He had heard about an old wizened-black woman who was supposedly a 161 year-old nurse to General George Washington. Joice Heth was first displayed in New York City and then moved to Boston, Massachusetts. Upon autopsy, this human relic was determined to be around 70 years old and the hoax was exposed. Barnum insisted that the papers he acquired when he purchased Joice in Philadelphia, Pennsylvania, were authentic.

It was through his advertisement of Joice that Barnum first realized he could be profitable from human curiosity. As the years passed, Barnum obtained many "freaks" and oddities that he put on public display.

In 1842, Barnum purchased John Scudder's American Museum. Between 1842 and 1868, the museum suffered huge losses from two fires. It is estimated that during those years, Barnum had enticed 82 million visitors into his halls and to his other enterprises. Charles Sherwood Stratton (1838-1883), better know as General Tom Thumb, was an American midget. As a youth, Tom measured only 25 inches tall and weighed 15 pounds. He was so bright, that at age six, P. T. Barnum had convinced his parents to let him join his museum in New York City. In 1844 Barnum took Tom Thumb abroad for a triumphal tour, during which he gave a command performance before Queen Victoria. In 1863, Stratton married Lavinia Warren (1841-1919), another one of Barnum's midgets. In later life, Tom had grown to 40 inches in height and weighed 70 pounds. Some of his furniture and his coach are still on display at the Barnum Museum, Bridgeport, Connecticut.

After 44 years of marriage, Charity Barnum died in 1873. The following year, Barnum, then 64, married 24 year-old, Nancy Fish, the daughter of a British admirer, for his second wife.

Although well-know and popular through his attractions over the years, Barnum did not become a circus showman until he was past the age of sixty. He did not invent the modern circus, but, in partnership with the retiring entrepaneur, James A. Bailey, he gave the American circus its gigantic size and its most memorable attractions. The highlight of his circus career was the purchase of Jumbo, the 6-� ton elephant he purchased in England.