Chicago CTA guide: Chicago Transit Authority maps & information

Chicago was built on a grid system that makes it one of the easiest big cities to navigate. Every half-mile, which is about equal to four city blocks, there is a major thoroughfare. The starting point for the grid is at the intersection of State and Madison in the downtown Loop. State Street runs north/south and Madison runs east/west. Addresses typically increase by 100 with each block (except downtown where streets do not always correspond to a full block). Slightly off-setting the perfect grid are diagonal streets, such as Milwaukee, Archer, Lincoln and Clybourn avenues. These main arteries of travel are convenient to cut across the city, but can make certain intersections (where six streets merge) quite chaotic.
When it comes to public transportation, Chicago has an efficient network of above-ground and underground trains, nicknamed the "L," as well as a full system of buses to take you where you need to go. The L routes convene in the center of the city where the trains “loop” around downtown. Buses fill in the gaps where the L lacks service and provide an easy means for getting from point A to point B.

Chicago Maps (CTA)