I'm definitely no expert, but to me it seems that its such a late piece, how can you say where it was made? A maker trained in the southern style of gun making could have been taught by his dad, who used to be a gun maker from Tennessee, but who moved to Illinois in the mid 1800s or even later. Or maybe he moved to Iowa, or then again maybe he stayed in the southern mountain region all along. I don't think you can rule anything out, but I'd hazaard a s.w.a.g and say west of the Appalachians for sure, and thats about it. That said, it seems that there are lots of southern traits in the piece...just wondering but do you know if the triggers are bolted through the tang or held in by the guard? Just curious how late that feature was carried on in pieces like this...especially the commercial hardware variety. I'm assuming from your description of the wood screws in the comb that the triggers free float and are held by the guard.
tca