Folsom is a census-designated place (CDP) in Delaware County, Pennsylvania, United States. It is part of Ridley Township. The population was 8,323 at the 2010 census.Folsom is located in northern Ridley Township at 39°53′31″N 75°19′34″W (39.891978, -75.326231). It is bordered to the northwest by the borough of Swarthmore, to the north by Springfield Township and the borough of Rutledge, to the east by Pennsylvania Route 420, to the southeast by the borough of Prospect Park, to the south by the borough of Ridley Park, and to the southwest by Woodlyn in Ridley Township. Folsom is 11 miles (18 km) southwest of Center City, Philadelphia.According to the United States Census Bureau, the Folsom CDP has a total area of 1.2 square miles (3.2 km2), all of it land.