The line was added to the system on November 17, 2006, with the completion of the Southeast Corridor as part of the T-REX Project.

Currently, the E Line is operating at a 60 minute headway due to repairs of the coping panels on the Southeast Corridor.

It shares track with the D Line from Union Station to I-25 & Broadway, then diverges by a level junction onto a flyover, and then parallels Interstate 25 from there to Lincoln Avenue in Lone Tree.

[2] On May 17, 2019, it was extended south by 2.3 miles (3.7 km) to RidgeGate Parkway station in Lone Tree.

It included three new stations, Sky Ridge, Lone Tree City Center, and RidgeGate Parkway, the latter with a 1,300-stall parking facility.