I've never owned or even fired one for that matter, but have noticed them around a lot and are extremely well-known in the black powder community, more so than any other model I've ever notice before.
What is it that makes it such a standard? View attachment 160713
View attachment 160715
There is not a lot of difference between Hawken-styled rifles and other half-stocked rifles that were coming into vogue back east, except that the half stocked plains rifle generally ( but not always ) had a bore of .50 or over.
Some of the rifles made expressly for plains use had more wood in the wrist area, presumably to make them a little less prone to breakage if dropped from a running horse or rolled over on by a horse or mule.
From what I have seen in museums, and surviving specimens elsewhere where at least some documentation exists, the average explorer/trapper/camp worker, hunter used a non-Hawken rifle or smoothbore just like most of his brethren used back east. Double barreled shotguns were apparently more prevalent than is commonly thought.
People who know more about this than I do day the official Hawken Plains Rifle did not start hitting the market in small numbers until near the end of the fur trade era.