Michael Schultz was to be the original director, but left before production started due to "creative differences".
While filming at the North Dakota State Penetentiary, the production hired extra security--not only for the cast and crew but also for the equipment and tools, which were inventoried and locked up every night. The only women on the set, writer and producer Mildred Lewis and actress Vonetta McGee, were each assigned personal guards. Filming had to be suspended at mealtimes and before the 7:00 p.m. lock-up each night.
The production began without any announcements in the trade press to maintain secrecy.
Filmed independently in early 1976 on a budget reportedly under $1 million. It wasn't until February of 1977 that "Daily Variety" announced Warner Bros. had acquired worldwide distribution rights.