Feature-film debut of Catherine Burns, in a role that would earn her an Oscar® nomination as Best Actress in a Supporting Role.
There was a screening in Los Angeles in 2012 wherein Barbara Hershey was a guest. She revealed that she, Bruce Davison and Richard Thomas didn't get along but for the sake of the film. She said: "Bruce and Richard might say something different, but I think Frank was encouraging us more to be into our characters than to bond. He was sort of isolating us from our lives.... We had interaction with each other, but it wasn't like we were a close-knit group."
Ralph Waite played father to Richard Thomas in this movie, then went on to play his father again in The Waltons (1972).
A subplot involving a wounded seagull affected Barbara Hershey sufficiently for her to change her surname to Seagull for a couple of years.
Last Summer (1969) was one of a handful of high-profile X-rated movies that were released in 1969, along with the Best Picture Oscar® winner Midnight Cowboy (1969) and Haskell Wexler's docudrama Medium Cool (1969). The scene was edited shortly after its initial theatrical release so the film could receive an R-rating, making minor cut to language and the rape scene, though this version still contained nudity and strong language. When the film was occasionally broadcast for television, a further-censored PG-rated version was presented, which cuts all nudity and heavily edits the scene of Rhoda's rape.