For those curious about the density of the area in question, here area couple maps showing the density at the Census Block Group level, which is the finest-grain data I have access to, and is smaller than Census Tracts. If there are even pockets of density, they should show up in these maps.
First, a map of the area in question. As you can see from the legend, there are no block groups on the map that are anywhere near as dense as normal advice for heavy metro-style rain would normally be advisable for. The few yellow ones are still just barely above the green areas, and the green areas are at good bus service densities - maybe even BRT levels, but certainly not rapid rail transit levels. I've drawn in the three alternatives (sorry it's just by hand).
For comparison, here's the area in context of the rest of Chicago. You can see that the density of the city follows the lakefront, is more on the northside, and roughly follows existing rail routes. Where population densities are lower and rail is heavy, such as the Loop, there are known large employment centers where employment density often exceeds 50,000 jobs per square mile.