Sandy Dennis was born at Mary Lanning Memorial Hospital in Hastings, Nebraska, on April 27, 1937. Her parents were Jack and Yvonne Dennis. Her brother, Frank, was eight years old. Sandy’s paternal grandparents, Frank and Fannie Dennis, as well as maternal grandparents, Fred and Bessie Hopp, also lived in Hastings. Sandy lived in Kenesaw for about a year, in 1943, but remained in Hastings after that until 1946, when she moved to Lincoln, Nebraska.
Although residing in Lincoln, Sandy returned to Hastings often to visit her family. She graduated from Lincoln High School in 1955, attended Nebraska Wesleyan University for one semester, and then University of Nebraska for one semester. In 1956, she appeared in Rainmaker at the Lincoln Community Playhouse and was given the Best Actress Award for her performance. She left Nebraska shortly afterward to pursue an acting career in New York.
In New York, she studied with Herbert Berghof and after appearances in several stage plays and television programs, was cast in a small role in the movie Splendor in the Grass in 1961. She won two consecutive Tony Awards for her performances in A Thousand Clowns in 1963 and Any Wednesday in 1964. In 1966, she was given an Academy Award for best supporting actress in Who’s Afraid of Virginia Wolfe. In 1967, Sandy was awarded a prize at the Moscow Film Festival for Up the Down Staircase and in 1970, was nominated for a Golden Globe Award for The Out-of-Towners. Sandy continued to work in stage, television and films in the United States, Canada, and Great Britain.