Baron Lumber Mill
The Baron Lumber Mill is an Outpost in Jacob's Region, and a prerequisite for recruiting Jess Black. There are lots of sniper perches and catwalks here (a perfect outpost to attack with Jess, if you somehow already had her).
As it is, you can do pretty well for stealth just sniping from the wooded hill north of the site- just remember to keep changing positions. You might also want to keep Grace or Peaches on standby for any hostiles that get away from you. This is particularly true for the lone heavy mixed into the bunch here. If you miss your first shot, call up a pro for the second
Killing the last hostile completes the location.
You'll see Jess freed in the liberation cutscene. Note that, right by where she starts out, is a table with a regional map and a key. It's worth grabbing both.
The key opens the front office, which contains the safe.