CTA is Chicago Transit Authority. CTA runs a total of eight different transit lines,
Red Line - 24-hour train service between Howard on the North Side and 95th/Dan Ryan on the South Side via subway through downtown Chicago,
Blue Line - 24-hour rapid transit train service between Chicago-O'Hare International Airport(Opens in a new window) and the Forest Park terminal, via downtown Chicago,
Green Line - Rapid transit train service between Harlem in Forest Park, IL and Oak Park, IL to 63rd Street on Chicago's South Side, through downtown via the Lake and Wabash sides of the Loop ‘L’,
Brown Line - Rapid transit service, daily, from Kimball to downtown (with certain late nite trips between Kimball and Belmont only),
Purple Line - Rapid transit train service between Linden (in Wilmette) and Howard (in Chicago) via Evanston. Additionally, during weekday rush-periods, express service continues to downtown Loop,
Orange Line - Rapid transit train service between Midway Airport and downtown (Loop), and provides service to Chicago's Southwest Side,
Pink Line - Rapid transit service, daily, from 54th/Cermak (in Cicero, IL) to the downtown Chicago Loop,
Yellow Line - Rapid transit train service between Dempster-Skokie (in Skokie, IL) and Howard (in Chicago), with connecting service to downtown Chicago via Purple Line Express or Red Line.

It is possible to download the following datasets from this webpage.
- kml dataset includes Bus Garage Locations, Bus Routes, Bus Stops, Bus Turnarounds, Fare Media Sales Location, 'L' (Rail) Lines, 'L' (Rail) Stations, Park and Ride Locations
- Ridership dataset includes Annual Boarding Totals, Bus Routs-Daily Totals by Routes, Bus Routs-Monthly Day-Type Averages & Totals, Bus Stop Boardings, Daily BoardingTotals, 'L' Station Entries - Daily Totals, 'L' Station Entries - Monthly Day-Type Averages & Totals
- System information dataset has a list of 'L' stops along with some developer tools like Bus Tracker API, Customer Alert APIs, GTFS(Google Transit Feed Specification) data, Train Tracker API