Lansdowne is a borough in Delaware County, Pennsylvania, United States, located 6 miles southwest of Center City Philadelphia. It was named for the Marquess of Lansdowne. As of the 2010 census, the borough had a population of 10,620. Lansdowne grew quickly in the early part of the twentieth century, when a railroad stop was established near the intersection of Lansdowne Avenue and Baltimore Pike. The borough is primarily residential, with a commercial center near the original railroad stop.