Ohio: Before the New Deal, the most Republican part of the state was always the northeastern "Western Reserve", while the most Democratic area was most of the German-settled western counties (i.e. John Boehner's district). Now it's the reverse.
Illinois: The northern counties were among the most rock-ribbed Republican counties anywhere in the nation, while the southern counties usually voted Democratic. However, in the last few presidential elections the southern counties have been providing the largest GOP pluralities.
Missouri: The southern-settled "Little Dixie" north of St. Louis was always the most Democratic area of the state. Now it votes Republican (at least in the presidential election).
My ancestors lived in Scott County (borders Illinois's southern tip) from the 1830s onward (some of them still live there). They were consistently Republican/Unionist over that entire period, at least according to my grandmother and great-aunt's recollections. (Though the ones that currently reside in that area actually tend to vote Democratic).
Scott County isn't in Little Dixie. It was also historically Democratic, though.
