Unless they are wiped out by a cattle-tick born pandemic, as documented when the Texans moved big herds into Montana. Within 2 years there were only buffalo bones left scattered all over the Northern Herd territory. Probably happened with the Southern Herd too, but that's not documented.
There was no increase in RR shioments of hides from Mt. , but hundreds of thousands of bison were just gone, that quickly. The bone collectors then had a few good years.
Try to convince someone that wants to believe the White man shot them all. As if a relatively few white folks could wipe out millions of bison that were increasing their numbers by 25% or more every year. Tick fever introduced by Texas and Mexican cattle did it.
History is full of lies.
