The Chicago Transit Authority or CTA (transitchicago.com), is the operator of mass transit consisting of buses and the ‘L’ (heavy-rail system) within the City of Chicago and some surrounding suburbs. The 106.1-mile (170.8 km) Chicago ‘L’ (or EL) system is 56.4 miles (90.8 km) elevated, 35 miles (56.3 km) at grade, and 11.4 miles (18.3 km) underground (subway).

The Loop (historically Union Loop) is the two mile circuit of elevated railroad consisting of nine stations that forms the hub of the ‘L’ rapid transit system in Chicago, Illinois. The Loop is so named because the railroad loops around a rectangle formed by Lake Street (north side), Wabash Avenue (east), Van Buren Street (south), and Wells Street (west).

Five of the eight ‘L’ lines use the Loop tracks. Two of the remaining three lines, Blue Line and Red Line, run underground through the center of the loop, connecting to loop stations. The Yellow line is the only CTA line that does not run on or connect to the loop.

The Red Line route (Termini: Howard to 95th/Dan Ryan) is 23.4 miles (37.7 km) long with 33 stations, from Rogers Park (Howard Street Terminal near Evanston) on the City Limits north, through downtown Chicago (State Street Subway), and to Roseland (95th/Dan Ryan) on the south via the Dan Ryan median. The Red Line is CTA’s busiest rail line, serving an average of 248,844 passengers each weekday as of October 2009. The Red Line runs 24 hours/365 days a year. The Red Line stops near Wrigley Field and U.S. Cellular Field.

The Blue Line route (Termini: O’Hare to Forest Park) is 19.5 miles (31.4 km) of trunk line (elevated/underground) in the Chicago Transit Authority’s rapid transit system which extends from O’Hare International Airport at the far northwest side of the city via the Kennedy Expressway Median, through Chicago’s Loop and downtown via the Milwaukee-Dearborn-Congress subway, and across the West Side to its southwest end at Forest Park (Congress). The Blue Line is the CTA’s second busiest rail line, with an average weekday ridership of 154,012 as of October 2009. The route’s full length is 34.6 miles (55.7 km) with a total of 33 stations. The Blue Line runs 24 hours/365 days a year.

The Green Line (Termini: Harlem to Ashland/63rd to East 63rd/Cottage Grove Station) is known as the Chicago ‘L’ and is the only completely elevated route in the ‘L’ system. The Green Line uses the transportation system’s oldest segments extending 20.8 miles (33.5 km) with 29 stops between Forest Park and Oak Park (Harlem/Lake), through Chicago’s Loop, to the South Side and Englewood (Ashland/63rd) and Woodlawn (Cottage Grove/63rd). A 30th station at Morgan and Lake Street in the west Loop is scheduled to open in 2012.

The Purple Line is a 3.9-mile (6.3 km) branch line on the northernmost section of the Chicago ‘L’ rapid transit network. The Purple extends south from the Wilmette terminal at Linden Avenue, passing through Evanston to Howard Street, on Chicago’s northern city limits. Average weekday ridership on the Purple Line was 39,799 as of October 2009.

The Purple Line operates weekdays 4 a.m. to 1 a.m., Saturdays 5 a.m. to 2 a.m., and Sundays 6 a.m. to 1 a.m.

The Purple Line Express … During weekday rush hours (approximately 6 a.m. to 10 a.m. and 3 p.m. to 7 p.m.), the Purple Line extends another 10.3 miles (16.6 km) south from Howard Street to downtown Chicago running express from Howard Street to Belmont Avenue, and then making all local stops to the Loop. The express service is known as the Purple Line Express, while the Linden-Howard shuttle service is the Purple Line Shuttle.

The Purple Line is useful for reaching officially purple Northwestern University (Davis, Foster, and Noyes stops in Evanston), including the athletic arenas (Central Street), and the Bahá’í House of Worship (Linden stop).

The Brown Line route (Termini: Kimball and Lawrence Terminal in Albany Park/Loop) is an 11.4-mile (18.3 km) route with 19 station between Albany Park on the north and downtown Chicago. The Brown Line operates to the Loop weekdays and Saturdays from about 5am to 12:30am and on Sundays from 7am to midnight. The Brown Line Shuttle service, running only between the northern terminus Kimball and Belmont, runs from about 4am to 5am and about 12:30am to 2:30 am on weekdays and Saturdays, and about 5am to 6am and about midnight to 1am on Sundays. At Belmont, southbound riders can transfer to the 24-hour Red Line. Check ctatransit.com for the latest updates.

The Pink Line route (Termini: 54/Cermak to The Loop) is an 11.2-mile route that share tracks with the Green Line. Average weekday ridership on the Pink Line is 29,242 as of October 2009.

The Yellow Line route (Termini: Howard Street Terminal to Dempster Street Terminal in Skokie) is a 5.1-mile (8.2 km) non-stop shuttle route with only the two terminus stations. At the Howard Street terminus at 1649 W. Howard Street there is a transfer station for the Red Line and the Purple Line. The Yellow Line is the only CTA line that does not go to The Loop. Service is provided Daily, Monday-Friday between 5am and 10:30pm, Saturday-Sunday 6am and 11pm with an average weekday ridership of 4,980 as of October 2009.

The Orange Line route (Termini: Midway International Airport to The Loop) is a 12.5-mile (20.1 km) route with 17 stations. The Orange Line has an average weekday ridership of 55,787 as of October 2009.

The CTA provides service to Chicago and 40 surrounding suburbs. The CTA provided a total of 521.2 million rides in 2009, a 1 percent decrease (5.1 million fewer rides) over 2008 numbers.

CTA operates 24 hours each day and on an average weekday provides 1.7 million rides on buses and trains. It has approximately 1,800 buses that operate over 140 routes traveling along 2,230 route miles (3,658 km). Buses provide about one million passenger trips a day and serve more than 12,000 posted bus stops. The Chicago Transit Authority’s 1,190 train cars operate over eight routes and 222 miles (357 km) of track. Its trains provide about 650,000 customer trips each day and serve 144 stations in Chicago.