Chicago has 630 car share locations. As Walk Score notes, the top three neighborhoods for car sharing are the Loop, Lake View and the Near North Side. But if you dig a little deeper and look at a map of Zip Car locations, you’ll see that, as with most of the city’s hip urban amenities, car sharing is unavailable west of Milwaukee Avenue or south of Hyde Park.
The city’s southernmost Zipcar is at Midway Plaisance. Excepting the airports, its westernmost Zipcar is at Lawrence and Kimball.
A blog post on Slate calls the rankings misleading, because Chicago is so much larger and less dense than some of the cities it outranks, such as Washington, D.C., Portland and Boston.
Chicago has 630 car shares but it also has 2.7 million residents and 227 square miles of land area. DC has about a quarter of Chicago's population and just 61 square miles of land to contain its 521 car shares. Portland has about as many car shares as DC (531) but fewer people and a much larger area. It's clear that either Portland or DC is a more "car share dense city" than Chicago, and then the question of comparing DC to Portland is how much do you weight population versus land area in assessing this kind of thing. In my experience as a Zipcar user, both the per capita quantity of vehicles (which determines scarcity) and the per square mile quantity of vehicles (which drives convenience) are important factors.
But this ignores the fact that there are three Chicagos -- a white, modern Chicago along the lakefront; a white, traditional Chicago on the Northwest and Southwest sides; and an impoverished, black and Latino Chicago on the South and West sides. Zipcar is marketed only to the first, which occupies a geographic area equal in size to those smaller cities. If you live there, Chicago is one of the top car share cities. If you don’t, it’s not a car share city at all.