Since it was created in 1959, Second City has produced some of the most inventive and famous comedians and comic actors in the United States. Many alumni went on to be featured players in "Saturday Night Live" and from there became movie stars. Among the graduates who worked with Mr. Sills are John Belushi, Bill Murray, Gilda Radner, Stephen Colbert, Mike Myers, Mike Nichols, Barbara Harris, Alan Arkin, Del Close, Dan Aykroyd, Harold Ramis, George Wendt, Shelly Long and Elaine May.

Second City grew out of the Compass Players, a 1950s cabaret revue show that was started by some undergraduates at the University of Chicago. The group is credited as being "the first theatre company to use improvisational techniques to create the current-events-driven, sketch-comedy format," according to the Chicago Tribune. Among the Compass members at the time were Mr. Sills, Nichols, May and Harris, who later became Mr. Sills' first wife.

The group later adopted the name The Second City, taken from a New York essay in which writer A.J. Liebling looked down his nose at the goings-on in Chicago. With Bernie Sahlins backing the effort with funds and solid management, the first Second City revue, premiered in 1959 at 1842 North Wells Street. The annual revues moved to 1616 North Wells in 1967. A Second City production reached Braodway in 1961, with Mr. Stills directing. Later, Mr. Sills founded the Story Theatre, which improvised plays from stories, myths, folk tales, and legends.

One Story Theatre production came to Broadway in 1970 and ran for 243 performances. The cast included Melinda Dillon, Paul Sand and Valerie Harper. It was nominated for a Best Play Tony Award. Sand won for Best Featured Actor in a Play. The show later ran in repertory with Ovid's Metamorphoses.

Mr. Sills was heavily influenced by his mother, the drama theorist and educator Viola Spolin, who created hundreds of improvisational games. In the 1970s, when he moved to Door County, WI, where he worked extensively as a writer and teacher, he continued to develop and refine his mother's initial work in "story theatre." Mr. Sills also is survived by a brother, William; a son, David Michael; and four daughters, Rachel, Polly, Aretha Amelia and Neva. The funeral service will be private. Plans for a public memorial service are pending.