Willow Grove is a census-designated place in Montgomery County, Pennsylvania. A community in Philadelphia's northern suburbs, the population was 15,726 at the 2010 census. It is located in Upper Dublin Township, Abington Township and Upper Moreland Township. Willow Grove was once known for Willow Grove Park, an amusement park that was open from 1896 to 1976, now the site of Willow Grove Park Mall. Willow Grove is considered an edge city of Philadelphia with large amounts of retail and office space.Naval Air Station Joint Reserve Base Willow Grove is located northwest of the Willow Grove CDP in Horsham Township. NAS JRB Willow Grove transitioned into Horsham Air National Guard Station in September 2011.