This story is based on a true incident that occurred in 1953. Many of the St. Louis Metropolitan Police officers and bank employees play themselves doing what they did during the actual robbery.
Tower Grove Park where the bank robbers meet is in the same neighborhood Virginia Mayo lived as a child.
Steve McQueen was still quite unknown during this film's shooting despite the success of The Blob (1958) one year earlier.
John says that he was born in 1897. The actor playing him, Crahan Denton, was born in 1914. He died of a heart attack in 1966 at age 52.