Re Lincoln, please see my original post.
If one's "home" is in the middle of the thing, then that can assert some pretty strong tugs.
I'd venture to say that in many respects in the 1860s, the loyalty to one's state oft took precedence over one's fealty to even the national government. Such was it with Lee and the thousands of others who, even torn between loyalties, struck South.
In that respect I would have been one of them.
May we never have to so choose again.
But it wasn't loyalty to a state which mattered so much as loyalty to the "peculiar institution" of slavery.
That's why it's estimated that even though all-told nearly a million Southerners served in Confederate armies, still 450,000 more served in Union Armies, in units from every Confederate state.
About 150,000 of those Southerners in Union units were black, former slaves, the other 300,000 whites from Unionist sections of their slave-states.
These included:
So, joining the Union Army in a slave-state could be difficult and dangerous, but many Southerners despised slavery enough to accept the risks.
An interesting Union unit is the First South Carolina Volunteers.
They were probably the first ever unit to actually increase in numbers with most of its battles. Upon seeing them in action, nearby slaves would drop their agricultural tools, pickup the weapons of casualties (from both sides) and follow the soldiers back to their camp after the battle.