I can vouch for that...

Many of my favorite backpacking trips took place in and around the Grand Canyon. Wonderful skies.

The best skies I ever saw were in Alaska, of course.... and not really backpacking although I did hike a few overnighters. It's so mountainous there that you really do not not have to get very far at all from Anchorage or Fairbanks to see magnificent skies. (Never been to Fairbanks but got very close on one hike). But in honestly I believe I preferred the Grand Canyon area. - JamesJM