**Sidney Blackmer (1895-1973)** was a prolific American actor who was active for over five decades. His film career spanned from silent movies to the 1960s, appearing in hundreds of films.

Specializing in character roles, he distinguished himself in portraying authoritarian figures, powerful men, corrupt politicians, and individuals with a sophisticated but often sinister aura. His screen presence often lent a controlled intensity and subtle ambiguity to his characters.

Among his most memorable appearances were those in *In Old Chicago* (1938) as the cynical Boss Hogan, *Duel in the Sun* (1946) as Senator McCanles, and above all as the terrifying Roman Castevet, leader of a satanic cult, in the classic horror film *Rosemary's Baby* (1968) by Roman Polanski, his last major film role.