Chicago’s River flows backwards because the city was undergoing huge typhoid and cholera outbreaks due to their incredibly poor sanitation management. This sanitation management, or lack thereof, caused them to just dump all of their waste into the Chicago river which polluted it so heavily in human waste that they were incapable of seeing blue water. There was a large debate over the ecological disasters this would impose on the people living further down the river in Illinois, but their concerns were ignored and the project went ahead.
There were a lot of different tickets used, A Washington, Columbus, Lincoln, and an American Indian Chief were all general admission. Benjamin Franklin was for complimentary entrance, and Handel was for the music. These tickets only represented a fraction of the primarily used ones because all of these were paid in advance tickets. The vast majority of the 21 million paid admissions were day of sale tickets, accounting for 15 million of them.
I managed to find these maps for Chicago’s ethnic diversity, I found one on a University of Minnesota webpage talking about the Hull House and another from an American cartography website.