Most certainly interested in this, so in the spirit of jolly cooperation I'll toss in an enclave idea to get started.

Missouri could be a very interesting locale (bootheel especially), as it's prime real estate for disaster. Flooding, tornadoes, dangerous wildlife and close enough to the east-west divide to have the powers that be breathing down our necks. Not only this, but due to the inherent risk of overland travel various 'river gangs' could be vying for dominance of the waterways, either as a means of navigating the state proper or smuggling goods in and out of the Mississippi cordon.

As for the enclave itself I'd suggest that as the borders were redrawn a splinter faction the U.S. Army Corps of Engineers fortified the [url=https://en.wikipedia.org/wiki/Truman_Reservoir]Truman reservoir.[/url] It's a bit further west but being on the Osage means that we'd have to contend with trouble coming out of state over the Marais des Cygnes and are smack dab in the center of anything floating up or down our little slice of the apocalypse

As an aside and play on post-fall nomenclature I'm thinking we could be nicknamed either "the Dammed" or "the True Men" by other groups/settlements.