When I attended the Univ. of Illinois in the early 50’s there were already several openly Communist professors and associate professors in residence. Chicago and Illinois have been the incubator of Marxism in the USA for at least 100 years.
I learned all about communists in Chicago from The Venona Secrets by Romerstein and Breindel and The Communist by Kengor. The entire city has been infested with them for a hundred years.