The first exchange of dialogue in this movie is between Jack Elam and Clayton Moore. That right there ought to be enough to tell you whether you'd want to watch it, even though to be honest, and to get this out of the way right from the start, it's not very good. This is another Western that I'd never heard of before watching it recently.
It's based on the real-life activities of Sheriff Henry Plummer, the notorious outlaw sheriff whose gang of thieves and cutthroats plagued the Montana gold fields, even while Plummer was pretending to be trying to catch them. In this version, Lon McCallister plays a young man who is duped by Plummer (played by an old, paunchy Preston Foster) into becoming a deputy without knowing that he's really working for the bad guys. Cute Wanda Hendrix, wearing tight jeans, toting a Winchester, and looking like she stepped right off a RANCH ROMANCES cover, plays the daughter of a stagecoach station owner who is an uneasy ally of the outlaws. Inevitably, as it did in history, a group of vigilantes is formed to go after the outlaws, and that sets the stage for the final confrontation.
To get the bad stuff out of the way first, Clayton Moore is badly miscast as Plummer's chief henchman. With a mustache and goatee, he looks great, but he should have been the hero of this movie. When that distinctive voice of his rolls out, there's no way I could believe he's evil, although Moore tries hard, I'll give him credit for that. Which brings us to the movie's biggest weakness, bland little Lon McCallister, who might have made a halfway decent Audie Murphy-type hero if the script had given him anything to work with. Instead, his character is the dumbest, most useless protagonist I think I've ever seen in a Western. Honestly, Don Knotts in THE SHAKIEST GUN IN THE WEST is more of a Western hero than McCallister.
On the plus side, there's plenty of action, including stagecoach chases, gunfights, and some decent stunt work. Wanda Hendrix looks good, Jack Elam has a fine time playing a club-footed, hatchet-wielding killer named Gimp, and Preston Foster seems to be channeling Roy Barcroft and Charles King in his performance as Henry Plummer.
If you want a much better fictionalization of this story, read Robert E. Howard's great short novel THE VULTURES OF WAHPETON. I can't really recommend MONTANA TERRITORY as a movie, but I'm glad I watched it, for whatever that's worth.