There are so many ways to find demographic data. To prevent the task from seeming overwhelming, use this guide to sources and keep some basic strategies in mind. Ask yourself who would collect and distribute the kind of information you're looking for: government agencies? researchers? Don't hesitate to ask a librarian for help -- we're here to help (and we love the chase!).
City of Chicago Department of Planning and Development; Accessed via Wikimedia Commons 3/23/10