Upper Darby Township (often shortened to simply Upper Darby) is a home rule township bordering Philadelphia in Delaware County, Pennsylvania, United States. Upper Darby is 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. The township hosts a range of housing types including densely populated rowhouse sections similar to houses in neighboring West Philadelphia, tree-lined neighborhoods of turn-of-the-century single-family houses and mid-century developments. It is Pennsylvania's sixth most populous municipality.