In 1904, Olympic officials added freestyle wrestling, commonly known as "catch as catch can", to the programme. This style had far less history and tradition than Greco-Roman but did possess great popularity, having developed into a form of professional entertainment performed at fairs and festivals across Great Britain and the United States.

Source: the Olympics

Freestyle wrestling, one of three styles of wrestling used in international amateur competition (the others are Greco-Roman wrestling and sambo) under supervision of the Fédération Internationale de Lutte Amateur (International Amateur Wrestling Federation). It was derived from the English Lancashire, or catch-as-catch-can, style, in which nearly all holds were permitted.

Source: Encyclopedia Brittanica