Upper Darby Township (often shortened to simply Upper Darby) is a home rule township bordering West Philadelphia in Delaware County, Pennsylvania, United States. Upper Darby is also home to the Tower Theater, a historic music venue on 69th Street built in the 1920s. Upper Darby's population is diverse, representing over 100 ethnic cultures located within its densely populated, rowhouse streets. It is Pennsylvania's sixth most populous municipality. Located just 2.8 miles from Center City (downtown Philadelphia), and houses the western terminus of the Market-Frankford Line of the SEPTA mass transit system of Philadelphia, with the location at 69th Street in the heart of Upper Darby's principal business district. Multiple trolley and bus lines connect the 69th Street Terminal to all major SEPTA lines of Philadelphia.