Knapp, a classically trained actor, had an illustrious and wide ranging career on multiple continents before he was invited to Hawaiʻi in 1970 by Earl Ernst, the founding chairman of the UH Mānoa Department of Theatre and Dance. He became a mainstay in stage productions in the islands, working with many of the local theatres as well as the Honolulu Symphony, Hawaii Opera Theatre and PBS Hawaiʻi.

While Knapp brought many memorable characters to life on stage, he is perhaps best known for his performances as Father Damien, “the leper priest of Molokaʻi.” In 1976, Knapp directed himself in Aldyth Morris’ one-man show Damien, and performed the role internationally. Damien was broadcast nationally on PBS and won numerous national awards. Knapp was recognized by the Hawaiʻi State Legislature as “Hawaiʻi’s Adopted World Class Actor” for the role.

Other favorite roles at Kennedy Theatre included Henry Higgins in Pygmalion, the title role in The Miser and King Lear in Carol Sorgenfrei’s Cordelia Victorious.

Knapp received the UH Board of Regents Medal for Excellence in Teaching in 1977, and, in 2001, the Hawaii Shakespeare Festival was dedicated to Knapp in perpetuity.