http://home.nps.gov/applications/glac/c ... status.cfm
I routinely check the campsite status just to get a general gage of activity in the Park. For the first time I can find (even researching back in history at the site), the following campgrounds were all full for July 3rd 2009.
Many Glacier
Sprague Creek
Rising Sun
Two Medicine
Kintla
Avalanche
Apgar
Fish Creek
St. Mary
The campgrounds near the top of this list are often full in July/August, but for all of them, especially the ones towards the bottom of the list to be full, well, I can't find another date that it has happened.