You can actually go back to the 48ers, the European radicals who attempted a failed revolution and then fled for other parts, including the American midwest.
A number of them settled in Wisconsin and Minnesota where their affinity for socialism echoes to this day. They were instrumental in founding the Republican party and some of them found their way into the Union Army and the Lincoln administration. About 10% of the GAR was comprised of 48ers.
Schurz, Sigel, Blenker, Weber, Wedemeyer were among them. The contribution of the 48ers to the GOP is oddly ignored today, maybe because of their Marxist connections.
Interesting info, thanks.