The Newberry Library in Chicago a has long and storied reputation as having one of the premier genealogy collections. Their published catalog has been around for years. I recently discovered that Newberry has some very helpful Chicagoland resources at their Chicago Ancestors site where they suggest that you "discover the past by address." I wish there were more directories from other cities on-line. They are a great tool for researching families. Chicago Ancestors offers:
1. Chicago City Directory Street Guides
2. Chicago City Directories with PDF images of years: 1866; 1870, 1871, 1875, 1880; 1885; 1892; 1900; 1910; and 1923.
If you browse by collection (Browse tab at the top), there's an interesting resource that maps and documents homicides in the Windy City by location of the crime, and it also gives the name of the victim. I hadn't given crime records much thought when doing genealogy. I guess I never had reason to consider the obvious resource it can be.