Not that I'm doubting, but it sounds interesting...do you have a reference?
BTW, when I tell black coworkers that there were black families in Bismarck back then.....they look at me with incredulous faces.
Let me start his by noting that you grew up in an area just like Indianapolis. No one really knew that Zimmerman was a German name. Bismarck was renamed from whatever it had been named as a whistle stop on the railroad ~ to Bismarck ~ to attract German settlers. In the end they did manage to attract Russian Germans ~ see; http://library.ndsu.edu/grhc/research/scholarly/meetings_conventions/bloom.html