Then it should be a simple task of finding out just how many ranchers are left in Clark county then.
Is that going to tell us the reason why each of the former ranchers chose or were driven to leave?
I believe the BLM probably drove out some of the ranchers in Clark County, perhaps most.
Given the growth of Las Vegas, I'm not willing to state as fact that all of the former ranchers were driven out by the BLM unless I have a primary source. If you wish to state it as fact, please continue.