The poster showing Marilyn Monroe in a purple dress was created much later, after she became a household name. Monroe was basically unknown when the film was made in 1950 and only has a very small role. She certainly wouldn't have been given top billing at the time. In fact, she wasn't named on the original posters at all.
When the film was being prepared for a British bow, the producers hesitated because it was so full of American slang. At the time, films heavy with slang were usually re-dubbed for English audiences. Gerard Fairlie, the British author of the "Bulldog Drummond" adventure stories, was called upon as a consultant, and he advised against re-dubbing, even though some words would go right over the heads of British viewers. The film was not re-dubbed and earned good box-office returns in England.
Both actor/director John Huston and star Sterling Hayden were members of the Committee for the First Amendment, which stood against the blacklisting of alleged Communists working in the film industry during the Red Scare. Huston had never been a Communist, although Hayden at one point had been.
Marilyn Monroe regarded this as one of her best performances, particularly her final scene with Louis Calhern.
During the production, Walter Huston came to Hollywood for his son John Huston's 44th birthday party. Two days later, with John at his side, the legendary actor of stage and screen died of heart failure at age 66.