Glassboro is a borough within Gloucester County, in the U.S. state of New Jersey, within the Philadelphia metropolitan area. As of the 2020 United States census, the borough's population was 23,149, its highest decennial count ever and an increase of 4,570 from the 18,579 recorded at the 2010 census, which in turn had reflected a decline of 489 from the 19,068 counted at the 2000 census. Much of the recent and projected growth in Glassboro have been attributed to the growth trajectory of Rowan University, founded in 1923 and formerly known as Glassboro State College. Glassboro and surrounding Gloucester County constitute part of South Jersey.