I just finished watching the longest and worse movie that John Ford ever made: Cheyenne Autumn. All firearms, uniforms and military accoutrements were period correct. In the middle of the movie, a steam train pulled out of Dodge City with a cavalry troop on board.
AND THERE THEY WERE!!! Open top cattle cars! Loaded with hay and cavalry horses!
Now if a danged 1960's Hollywood Movie ain't proof, . . . then nothing is! :-)