There are places in Colorado that are a long way above sea level.
The lowest point in Colorado is 3300+ feet above sea level. So, yeah, all of them are...
Yes, I live in one. 7,600 feet. Unfortunately there are 14,000 ft. peaks just five miles to my west.
There are places in Colorado that are a long way above sea level.
It is 831 miles from Denver to LA.
From a 14,000 mountaintop, the horizon is 143 miles away.
If the missile explosion was at 313,000 feet (edge of space) and you were standing on top of a 14,000 foot high mountain near Denver, then the explosion would be just at the horizon.