OOC: The idea is they seceded because of more dependence on slavery
OOC: I figured that was probably the reasoning for it, but even so, slavery wasn't exactly all that strong even in KY compared to the Deep South, IOTL, let alone MO. And MO in particular, for that matter, was already getting a lot of German and other immigrants who weren't exactly amenable to slavery, a trend that was only on the increase by 1860 even IOTL(not to mention abolitionism would have gotten stronger, anyway). Even KY didn't secede despite some rumblings otherwise, and if not in 1860 than it would have been even more difficult in 1870, not less, for a myriad of reasons; maybe if KY somehow managed to elect a Fire-Eater as governor, they might still attempt to secede.....but such would be rather unlikely, and even if they did, there would be almost as much resistance to such, at least in some areas, as there was in Western Va. IOTL(hence, why West Virginia was created. And as for Missouri.....that case would require an altogether at least somewhat different socio-political situation than in OTL. So hopefully you've got a better idea of what I'm trying to point out now; it's up to you where you ultimately want to take this but I just wanted to help keep things plausible, that's all.