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is a township and the largest municipality in Delaware County and the 5th largest municipality in the Commonwealth of Pennsylvania.
It was founded during a split from Darby Township on August 30, 1736. However it was not incorporated under the home rule charter until 1907. Located just 5.8 miles from Center City, and bordering the Philadelphia city limits via Cobbs Creek, many of its residents work in the city. The east-west Philadelphia subway (the 'El') terminates at 69th street, Upper Darby's principal business district. Several trolley and bus lines connect 69th Street Terminal to the western suburbs of Philadelphia. As of the 2000 census, the township had a total population of 81,821. By 2005, the population was estimated at 79,620.
Upper Darby is 65% residential, 25% commercial, and 8% other. Because of a home-rule charter adopted in the 1970s, the township utilizes a mayor-council form of management (other "First Class" townships in Pennsylvania have a board of commissioners divided into wards, and "Second Class" townships having a board of supervisors, which are usually elected "at-large").
According to the United States Census Bureau, the township has a total area of 7.9 square miles (20.4 km²). The township lies on the edge of the Piedmont slightly above the City of Philadelphia (60 to 260 feet above sea level). The area is crossed by several small creeks. The borough of East Lansdowne, Pennsylvania is an enclave completely surrounded by Upper Darby Township; additionally, an exclave of Upper Darby Township is separated from the rest of the township.
The Census-Designated Place of Drexel Hill, Pennsylvania and the Community of Primos, Pennsylvania are part of Upper Darby Township.