The CTA Brown Line begins its runs at the Belmont terminus of the Ravenswood Branch, it makes 10 intermediate stops on the branch before meeting the North Side Main Line at Belmont (and runs concurrently with the rush hours Purple Line Express) taking local service over from the Red Line (that skips three stops before leaving the elevated and entering the Street Subway into downtown). Trains make 7 stops on this stretch before reaching the loop and reverse on the outer loop track as the only trains traveling the counterclockwise direction in full. On the Loop, Brown Line trains have there own platforms on the west (above Wells Street) and south (above Van Buren) quadrants of the loop and only share them with Harlem-bound Green Line Trains on other two. The line is over a century old with the North Side Main Line opening to Belmont in 1900 and the Ravenswood Branch in 1907. In terms of the number of stations originally on the line there were 29, 17 stations of these were on the North Side Main Line (just 7 are left today), but there was only one station closing on the Ravenswood Branch (Complete History on Chicago-L.org).

For many years train service on the Ravenswood Branch (called the Brown Line starting in 1994) during off peak overnight hours (today there is no owl service between 2:00am and 4:00am) was provided via a long shuttle train of sorts between Belmont and Kimball requiring passengers to transfer to the Red Line to reach downtown. From 1952 to until Summer of 2000 this included all Sunday Brown Line service. Today this is only done for about the last hour of service seven days a week (from about 1:00am to 2:00am, Weekdays and Saturdays, after midnight until 1:00am on Sundays) and for the first two hours (5:00am to 7:00am) of service on Sunday.

The Sunday through service to downtown was instituted due to record ridership in recent years, the Brown Line is the now the busiest Loop 'L' Line and third busiest 'L' Rapid Transit Line overall (the much longer Red and Blue lines that transverse downtown in their own subways are first and second). This resulted in the need for the Countdown to the New Brown: The Brown Line Capacity Expansion Project. This project rebuilt all of the Brown Line Stations north of downtown (on both the North Side Main Line shared with Rush Hour Purple Line Express Trains, and its own Ravenswood branch) to allow train lengths to be expanded from a maximum of six to eight cars. It also installed elevators (or ramps in the case of the four grade-level stations) to make every stop on the branch (off of the loop) ADA compliant and wheelchair accessible. Nearly every station was closed for between six months and a year to be rebuilt at some point between 2006 and 2009. Eight car trains began operating on the branch during rush hours on March 31, 2008 (with all non eight car stations closed for rebuilding). The last wheelchair elevators opened at Belmont and Fullerton on December 31, 2009 with a ribbon cutting on January 9, 2010 declaring the project complete.

Today virtually all stations on the line have wooden platforms (which is having an issue of premature rotting), short little canopies (for about two cars on average) held up by brown metal posts that extend from the sides of side platforms, and low silver metal railings along the platforms with silver lampposts rising above. Some of the stations have their original station houses but all have had fare control areas modified and enlarged.