Okay, no bites at all on LII #52. Here's a summary of clues and a new clue that should be helpful:

Something historical happened at this location.

It not IN Colorado.

Think BIG.

If it were in color the rocks would still be named the same as you see them. Hint: the site is named after the appearance of the rocks.

US leader HH (nothing to do with challenge #50 HH)