Betsy Blair, who played Clara, was almost not permitted to do the film by Hecht-Lancaster Productions and United Artists due to the 1950s Hollywood Blacklist. However, Gene Kelly, her husband at the time, basically blackmailed United Artists and Hecht-Lancaster into casting her, at the last minute, by threatening not to direct or star in any of UA's or Hecht-Lancaster's productions if she was not cast in the role.
Delbert Mann had no idea who to cast in the lead role, so asked his friend Robert Aldrich. Aldrich immediately suggested Ernest Borgnine. Mann was skeptical, as Borgnine was only known for playing heavies, but Aldrich convinced him. Borgnine regularly said that he owed his career to Robert Aldrich.
The only time in film history that the producers spent more on a film's award campaign ($400,000) than they did on making the movie ($343,000).
At 90 minutes long, this is the shortest of all films that have won the Academy Award for Best Picture.
A Moscow screening of the film during a 1959 cultural-exchange program made it the first US feature seen in the USSR since World War II.