It's hard to believe Robert Redford released this piece of garbage on the world. I'd thought more highly of him (until now).
The series is cheaply made, recycling the same footage over and over and over again. The continuity is lousy. So is the dialogue. The narration is trivial and repetitive. The clichés are endless, the scripting shallow. Many of the "facts" are non-factual (inaccuracies abound, as other reviewers point out). So it's historically suspect. All in all, the storytelling is at the level of an adolescent comic book.
In the end, this mini-series offers up the same shallow romantic crap about the West that's been around for decades. And it's badly made. Very disappointing. Sorry to say it, but Redford's judgment must be gone to put put his name on this work.
If you want to learn about the American West between 1865-1890, find something else. Or just watch a western movie; at least you'll be entertained.