It is the CTA's newest rail line and began operation for a 180-day trial period on June 25, 2006, running between 54th/Cermak station in Cicero, Illinois and the Loop in downtown Chicago.

The line runs on at-grade tracks parallel to Cermak Road from the terminal to about a quarter-mile (400 m) east of Cicero Avenue, then runs diagonally northeast until it reaches a corridor parallel and adjacent to 21st Street at Kostner Avenue.

It then continues east between 21st Street and Cullerton Street, climbing up from at-grade tracks to elevated tracks, through the North Lawndale, Little Village and Pilsen neighborhoods of Chicago, with stops at Kostner, Pulaski, Central Park, Kedzie, California, Western and Damen.

The line turns north near Paulina Street stopping at 18th and Polk stations, then crosses over the Eisenhower Expressway (Interstate 290).

It continues on the Paulina Connector to share tracks with the Green Line on Lake Street with stops at Ashland, Morgan and Clinton, before operating around the Loop clockwise.

In January 2006, the CTA held hearings on its proposal to reroute trains from 54th/Cermak via the recently rebuilt Paulina Connector to the Lake Street Green Line tracks, then operating around the Loop clockwise for the first time since Douglas trains began using the Milwaukee-Dearborn Subway in downtown Chicago on June 22, 1958.

[2] Non-rush hour trains would be routed via the Loop, Green Line tracks and Paulina Connector.

[3] The Pink Line began operation in June 2006, using the rebuilt Paulina Connector, which had not been used in regular revenue service for 48 years.

This is accomplished by routing all but 12 trains per day coming from O'Hare to Forest Park and adding entirely new service from the 54th/Cermak terminal in Cicero to The Loop via the Paulina Connector and the Lake Street branch of the Green Line.

Pink Line trains operate clockwise on the Inner Loop track via Lake-Wabash-Van Buren-Wells before returning to 54th/Cermak.