How long did Civil War era voting patterns persist in the North?

[TransfemmeGoreVidal]

I have a couple of related questions that I've wondered about for a long time.

1. It's pretty well-established that voting patterns in the south were until the Civil Rights Act largely the legacy of Civil War allegiances with the only Republican pockets being in areas that had been unionist strongholds during the war. Are there any equivalent counties in the North that were heavily Democratic because they'd been hotbeds of Copperhead/anti-war sentiment in the Civil War era? From some readings I've done it seems like there were elements of this in the state Democratic Parties of Ohio and Indiana.

2. In the aftermath of reconstruction is their any evidence that some northern Democrats who may have been Democrats because they were anti-war and favored an end to reconstruction may have shifted to voting Republican because of nativism/support for protectionism? Conversely did any Republicans who had only been Republicans because of abolitionism and/or support for the Civil War/Reconstruction shift to voting Democrat for the opposite reason? I know the Mugwumps are one example but I don't think that lasted beyond one election.

Apologies if any of these are dumb questions or have been answered before. They've just sort of been curiosities of mine for a while.