I have found history wise its complete garbage. But if you turn your brain off its okay, especially if there ain't nothing else to watch.
I'm not sure its factually based in anything, and while there were "Copperhead" Democrats in Upstate New York I'd say they were a minority after the guns sounded. Copperheads were more a Great Lakes States thing I think, but the movie only shows 4 Copperheads more motivated by the Constitution than the Confederacy and heavily discriminated against by their many, many Republican neighbors.