After he finished this film, Martin Scorsese screened it for John Cassavetes. Cassavetes, after seeing it, hugged Scorsese and said, "Marty, you've just spent a whole year of your life making a piece of shit. It's a good picture, but you're better than the people who make this kind of movie. Don't get hooked into the exploitation market, just try and do something different." Scorsese's next film was Mean Streets (1973).
The Reader Railroad was the actual name of the railroad where the train scenes were filmed. It opened in 1889 and is still in business, used at various times for freight, tourism and movie service. At the time of filming it was still regularly using vintage equipment, most notably steam locomotives.
The train sequences were shot first and they took about a week. This was done to get the most complicated element of the production, working with a moving train, out of the way first.
There was a rumor that Roger Corman's wife Julie Corman obtained the film rights to the story from Bertha Thompson herself after tracking her down in a San Francisco hotel room; she never actually met Thompson--because Thompson wouldn't open the door-but that rumor wasn't true. It may haver been a pre-release publicity stunt or maybe even a trick played on the Cormans by the true owner of the story, author Ben L. Reitman; the afterword in the fourth re-issue of the book "Boxcar Bertha" explained that the book is a work of fiction, and that the character Bertha Thompson was an amalgam of at least three women that Reitman knew, but was mostly modeled on a woman named Retta Toble.
In 1972 American-International Pictures distributed this film on a double bill with Killers Three (1968) starring Robert Walker Jr..
Barbara Hershey later called the film "a lot of fun even though it's terribly crippled by Roger Corman and the violence and sex. But between the actors and Martin Scorsese the director, we had a lot of fun. We really had characters down but one tends to not see all that, because you end up seeing all the blood and sex."
There are no characters in the film named Emeric Pressburger or M. Powell, and there are no such actors as Grahame Pratt or "Chicken" Holleman. Director Martin Scorsese added them to the cast list as a tribute to filmmakers Michael Powell and Emeric Pressburger.
The song 'Big' Bill Shelley and his guys are singing when Bertha rescues them is an A Capella by Vera Hall, called "Trouble So Hard".
Schedule for the movie was 24 days (according to director Martin Scorsese's commentary for Alice Doesn't Live Here Anymore (1974)).
The idea for the film was suggested by Roger Corman as a sort of "sequel" to Bloody Mama (1970), after Martin Scorsese became known for his work on Woodstock (1970).