In 1955, Sills and David Shepherd founded the Compass Players, the first improvisational theater in the United States, where he directed Shelley Berman, Mike Nichols and Elaine May. In 1959, Sills, along with partners Howard Alk and Bernie Sahlins, opened a theatre called The Second City where revues developed improvisationally were presented under Sills's direction. With early cast members Alan Arkin, Barbara Harris, Severn Darden, Mina Kolb and Paul Sand, success led to New York (a brief run on Broadway and a long one off-Broadway), London and world recognition.