I just went through the rule book but didn't see this explicitly stated, though it seems to be the case:

Once a Location becomes the Active Location, it is no longer considered in the Staging Area, correct?

I ask because I just played a game with the Spirit deck and I wasn't sure if Northern Tracker can place a progress token, after committing to a Quest, on the Active Location.

I'm thinking he cannot.

Thanks in advance!

You're right.

The active location is not in the staging area anymore. Northern Tracker's ability doesn't work on it.