Sidney Alderman Blackmer (July 13, 1895 – October 6, 1973) was an American actor who appeared in dozens of movies between 1914 and 1971, usually in major supporting roles. He was also a major Broadway performer. Blackmer was born and raised in Salisbury, North Carolina, the son of Clara Deroulhac (née Alderman) and Walter Steele Blackmer. He started off in an insurance and financial business but gave up on it. While working as a builder's laborer on a new building, he saw a Pearl White serial being filmed and immediately decided to go into acting. He attended the University of North Carolina at Chapel Hill. Blackmer went to New York, hoping to act on the stage. While in the city, he took jobs and extra work at various film studios at the then motion picture capital, Fort Lee, New Jersey, including a bit part in the highly popular serial The Perils of Pauline (1914). He made his Broadway debut in 1917, but his career was interrupted by service in the U.S. military in World War I. After the war, he returned to the theatre and, in 1929, returned to motion pictures and went on to be a major character actor in more than 120 films.He won the 1950 Tony Award for Best Actor (Drama) for his role in the Broadway play Come Back, Little Sheba, co-starring with Shirley Booth. In film, Blackmer is remembered for his more than a dozen portrayals of U.S. President Theodore Roosevelt and for his memorable role as Roman Castevet in the Academy Award-winning 1968 Roman Polanski film about urban New York witches, Rosemary's Baby, in which he played an overly solicitous neighbor. In 1919, Blackmer played a major role in the strike that led to the formation of Actors' Equity Association. A humanitarian, Blackmer served as the national vice president of the United States Muscular Dystrophy Association. He also helped start up the North Carolina School of the Arts. In 1972, he was honored with the North Carolina Award in the Fine Arts category. It is the State of North Carolina's highest civilian award. On his death in 1973, Blackmer was interred in the Chestnut Hill Cemetery in his hometown of Salisbury, North Carolina.

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