Philadelphia has a long history of operating trolleybuses, or "trackless trolleys", to use local terminology. Trolleybus wires once crisscrossed the entire city, but over the years, trolleybus service was gradually whittled down and replaced by diesel bus service, as was the norm in most major North American cities. The Southeastern Pennsylvania Transportation Authority, or SEPTA, continued to operate five trolleybus routes (routes 29, 55, 66, 75, and 79) into the new millennium using AM General 10240T vehicles originally built in the late 1970s. However, trolleybus service ended on routes 59, 66 and 75 in 2002, and the 29 and 79 met the same fate in 2003. Service on these five routes was subsequently provided by conventional diesel buses.

In February 2006, SEPTA placed an order for 38 New Flyer E40LFR trolleybuses to reinstate trolleybus service on routes 59, 66 and 75. These are state-of-the-art vehicles that can not only operate electrically under trolley wire, but also run for limited distances away from the wires using an auxiliary engine. The first pilot E40LFR (#800) arrived on SEPTA property in June 2007 for testing, and trolleybus service was restarted on the three aforementioned routes in April of 2008.

To commemorate the revival of trolleybus service in Philadelphia, the Friends of Philadelphia Trolleys chartered two New Flyer E40LFRs (#805 and #809) on June 1, 2008 for a special trip covering ground on routes 59, 66 and 75. Photos from this event can be found below.