We've seen a number of these huge beetles. Akmost 1" long.
We're on the front range in Northern Colorado at about 5200 feet. Never seen them before (that I noticed anyway) in 9 years here. Predictably, terrible fliers... just bomb into anything in their way (like me). Those antennae open up into beautiful fans, perhaps three times their folded width. Seem to see them more in evening time. This one sat totally docilely while I nudged and photo'd it. I think it hissed at me earlier but it was noisy; can't be sure.