Where is the ground in Chicago?

[faraway]

....My method would be to focus on the industrial area that I'm modeling not the city its self.

That is what most do by the pure practical reason of available space. Goose Island is very popular for an ISL: It has/had a lot of street running and provides a nice "big city" flair and you can run MP15AC from MILW, SOO and CP depending on the time you choose if you are an MP15AC lover.
Anyhow I am at the lumber district at the south branch of the river due to the nice CIRY switchers. The streets that really concern me are as flat as almost all industry areas. My initial question was triggered by an area some blocks north. The elevated streets are of no interest to my little layout but I was curious when I noticed the strange "gaps" between the houses and sometime between the house and the street/sidewalk.