Wyoming is the 44th state in the Union, admitted in 1890. It is the 10th largest state but the least populous one (50th). The capital and largest city is Cheyenne. Wyoming borders Montana, Idaho, Utah, Colorado, South Dakota and Nebraska.
 

Major Story Arcs

Marvel

In 1896, in a small town, the mutant that would one day be known as Absalom was to be hung.  He had wanted to take on Caleb Hammer, a legend in days gone by, but the old man didn't want any part of it.  Absalom shot Hammer in the back and was hung.  During the hanging, his mutant powers manifested, as bone spikes shot from his body.  He was freed from the noose, but not from the bullets the scared townspeople pumped into him.  He died but, being an External, came back to life a few days later.  He fled.
 
Dark Hole, Wyoming (a town that doesn't exist) was home to a passive energy facility that was destroyed by the Mutant Liberation Front.  The purpose: the MLF wanted Rusty and Skids to be released by Freedom Force.  If not released, they would destroy a similar facility for every day the two young mutants remained in custody.
 
Pine Bluffs, Wyoming (a town bordering Nebraska off I-80) housed a government facility in which the Mutant Liberation Front further made their point the next day.  The show of power was unwarranted, however, because the MLF just broke the mutants out themselves.

Belle Fourche Dam, Northwest of Reno Junction (the dam is actually in South Dakota, to the Northeast, but the writers put it in Wyoming), the government had placed a bomb, hoping to blame mutants for the destruction that would occur. X-Factor thought the bomb was planted by Mystique, as they had followed her there. She was actually just trying to stop the bomb from detonating. For reasons unknown, and by an attacker unknown, Mystique was attacked, allowing for an easy capture by Val Cooper.