He was born George william Duell in 1923 in Corinth, New York, to E. Janet (Harrington) and Leon George Duell, an employee of the International Paper Company. Sometime in his youth, his mother legally changed his name to Darwin william Duell. Duell never cared for his first name and thus always went by his middle name, william. Duell graduated from the Green Mountain Junior College (now Green Mountain College) (Vermont), Illinois Wesleyan University, and Yale University. A theater scholarship at Green Mountain College is named after him.