What was "Conical Frustum @ 200 10281"? I don't see where "aP" comes from.
Google "200 10281" then investigate more closely on Google Maps

Satellite version is clearer.
Yeah, I had real trouble with that one. I got some highway in Montana when I searched it and though it has something to do with it, since Montana was mentioned in other clues, like the one with a radio station, where btw I made the only mistake and wasn't able to solve the puzzle, since there were two radio stations listed on Wikipedia from Montana on the same frequency.