While that Straight Dope does explain *who* Mr. Damen was, it doesn't get into the *why* of the matter.
I was told many years back it was one of a many German-sounding streets renamed due to anti-German sentiment in the days leading up to the first World War. Schiller and Goethe, for example, remained, because those men were pacifists.
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Forgotten Chicago Sightings