Minnesota’s leftist politics far predates the anti-American propaganda in primary and secondary schools. It is related to European immigrants bringing socialism with them.
http://jcpa.org/dje/articles2/minn3.htm
...Minnesota is the archetypical example of a state informed and permeated by the moralistic political subculture — more so than any other in the Union or perhaps in the world...
Minnesota (and some neighboring states) was largely settled by immigrants from the Scandinavian countries and Germany. Minnesota became a state before the Civil War, before Marx had written the Communist Manifesto and Das Kapital. The historical timeline doesn't really mesh with the idea that the immigrants were predisposed to socialism.
Now of course there were socialistic or "progressive" ideas floating around the US from the Theodore Roosevelt era onward, but that would have probably affected later generations, after most of the earlier immigrants had passed on.