The political history of the Midwest has a long radical tradition that is anything but conservative, nor isolated to Minnesota. The origins of this history are in the founding of the Republican party in the Midwest/Illinois and run through William Jennings Bryan and Bob LaFollete, right up to Paul Wellstone and Tom Harkin.

This should not be confused with more modern interpretations of loaded words like progressive or liberal. There is actually a very clear strain of political and social activism that links this history together and is very Midwestern. The party labels and ideas have shifted but the underlying impulses are the same.

There are also some interesting crossovers with 19th century German philosophy and political thought that are linked to this heritage, and to the heavily German immigrant population in the Midwest.

If you are looking for the origins of it all, I recommend beginning with Eric Foner and his history, as well as learning about the German "48ers" influence on American political thought in the mid to late 19th century and the links between the progressive moment in the 19th and early 20th century with German philosophy and politics.