Now how does the clue, "Where cowboys corral mustangs and (66) Thunderbirds fly." fit in? I'm the clueless type.
Oh, sorry, didn't finish showing my work. The actual answers to the question are:
1. (generic) The place got its name because cowboys were said to use it as a corral for mustangs by fencing off the narrow neck leading to it. The story goes that one herd got left there without water and died, hence the name.
2. (virtual) the final sequence of "Thelma and Louise" was filmed here, including the drive off the cliff in Louise's (wait for it) 1966 Ford Thunderbird.