After nearly 40 years of service and millions of trips, the Chicago Transit Authority’s (CTA) 2400-series railcars made their last in-service run last week.

The cars, produced between 1976 to 1978, are being replaced as the CTA continues to upgrade its rail fleet as part of an aggressive modernization and infrastructure plan by Mayor Rahm Emanuel and CTA President Forrest Claypool. The CTA continues to add its newest, state-of-the-art railcars, the 5000-series, with more than 600 deployed to the Red, Purple, Yellow, Pink and Green Lines with a total of 714 of the new cars expected to be in place by the end of 2015.

To commemorate the 2400-series’ nearly four decades of service, the CTA will host ceremonial last rides on the Brown and Green/Red Lines on a train made up of 2400-series cars that have been restored to their original look inside and out.

Some fun facts about 2400-series railcars:

• Built by Boeing-Vertol, the car’s interior and exterior designs were developed by industrial design firm Sundberg-Ferar, who also worked on cars for the Washington Metropolitan Area Transit Authority, Bay Area Rapid Transit and Metropolitan Atlanta Rapid Transit Authority. The CTA’s 2400-series are the only heavy rail rapid transit cars Boeing ever manufactured.

• The interiors of the cars were a departure from previous series in several aspects and set the standard by which “L” cars interiors would be designed for the next few decades, featuring fiberglass seats with padded colored inserts, walnut grain-pattern wainscot panels with beige molded plastic upper walls and chocolate colored rubber floors. The 2400-series cars are notable as featuring a return to wide sliding side doors instead of bi-fold blinker-type doors, which had been featured on all “L” cars built in the preceding 30 years. These sliding doors allowed for freer passenger flow and were more suitable for access by persons with disabilities.

• The electrical equipment was updated and improved over that on the preceding 2200-series. A major change was the use of a motor-alternator to supply 230-volt 60-hertz alternating current power for all the auxiliary systems on the car, allowing less expensive components to be employed. These changes represented another step in the evolutionary path that eventually led to the modern 5000-series cars being delivered today, whose entire propulsion system is AC-powered.

• The 2400-series cars are one of the few car series to have operated on every line on the “L” system. At various points in their service lives, they were assigned to the lines that make up seven of the eight “L” services today. While never formally assigned to the Yellow Line, they operated there on rare occasions when substitute equipment was needed, since they were stabled in the same yard as the normal Yellow Line equipment.

• Two of the railcars were given to the Illinois Railway Museum, where they are on display today.

Nearly 200 2400-series cars were retired. CTA retains two dozen of the cars that have been modified to serve as maintenance/work trains. Some of the 2400-series railcars used in the CTA’s retirement ceremony will become part of its historic railcar fleet and will be used for special events and paid charters.