Task: Claim new lands.. "Too Narrow"

I'm level 20 now and have this task pop up about 5 levels ago. Since then I've defeated multiple camps as well as 3 of the "Boss" camps.

I had already defeated one of the boss camps before the mission showed up.
It says that I have 2 of 4 sectors even though I have defeated bosses in three (3) separate sectors.

Smack my butt and call me sally for assuming this would complete the mission???

Storehouses in them unclaimed sectors?

Ah ha! Thank you sir.
Not sure if that was in the tutorial, but that's the first/only building you can build in a new sector before developing it??

yes