Just a couple of thoughts. I know you don't want to make it all Civil war based but....
1) You mention a local fort. I can't believe noone seems to have made card models of all the civil war forts. I'd love to see someone do that. These would be relatively simple models for your giveaway idea. Of you did your local thought you could do different models throughout the ages if it changed much.
2) I love the Illinois History site with models of the local historic buildings.
Build Your Own Main Street I wish every state/town did this. Of interest to local inhabitants and modellers alike. A model of a local building every issue would be a great addition to your magazine.
3) Er.... that's it for now!!