I have a few from (2) vacations ago (Sept 16-24th 2006)
The crowds were very low at the beginning of the week- but picked up closer to the end of the week-
I think if we do Sept again it will be the week before the 16th next time- A friend of mine left on the day we came in and she said it was DEAD the week prior!
ahhhhh yesssss- an empty bus going to the AK! Sat 9/16