It's a lot of fun along the way, with plenty of violence and some good performances. There's a nice confrontation scene between David Carradine and his father, John, representing the railroads. Bernie Casey is pretty good, too, and when you have Barbara Hershey in the '70s, you don't even need acting. Not that she's not good. She is.
Maybe it's set in the '30s, but Boxcar Bertha is very much a '70s movie. Dig the poster, which is as '70s as you can get in its own way. The tagline. The heavy-handed symbolism. Great stuff.
Martin Scorsese directed, so you might guess that this was before he became the "name" director he is today. You should see it just to say you've seen his exploitation flick.