The surprises on that map are New Jersey, Minnesota and Washington state.
There was (to a lesser extent than the South) a solid north from 1860-1928. That explains Minnesota. New Jersey would often vote Democrat during this time, I'm not sure why. Washington State would probably have voted Republican if it was a State before 1890. It doesn't have all those earlier elections like Minnesota does to make it Republican over-all.
New Jersey was actually quite sympathetic to the Confederacy. They voted for McClellan, along with Delaware and Kentucky. I can only guess that it was a state similar to Delaware and Maryland at the time, which were culturally Southern.
