All-in-all it was enjoyable, and got most of the main points it was trying to tell. The attention to detail was terrible as others have mentioned (fat Native Americans with saddled horses, Jemimah Boone having her hair combed with something you could buy at Walmart, Kit Carson fixing his fence with a claw hammer bought from Lowes/Home Depot, etc.) I did learn about some things I didn't know, but I was a little disappointed about it missing some things I did know. For example, Daniel Boone's escape from a British-backed Shawnee war party during the American Revolution in order to run 4 marathons in 4 days barefoot while avoiding being tracked so that he could warn Boonsborough of the pending attack wasn't even mentioned. Additionally, there was far more to Jim Bridger than just leaving Hugh Glass behind as a youngster (especially since it's uncertain that it was even him). Episode 2 should have been about Hugh Glass and another episode dedicated to Bridger (Hugh Glass was the real-life man upon whom The Revenant and Man in the Wilderness is based).
Its worth a watch, but it's also worth looking into the rest of the stories.