The Delaware Valley is the valley through which the Delaware River flows. By extension, this toponym is commonly used to refer to Greater Philadelphia or Philadelphia metropolitan area ("the Delaware Valley Metropolitan Area"), which straddles the Lower Delaware River just north of its estuary. The Delaware Valley Metropolitan Area is located at the southern part of the Northeast megalopolis and as such, the Delaware Valley can be described as either a metropolitan statistical area (MSA), or as a broader combined statistical area (CSA). The Delaware Valley Metropolitan Area is composed of several counties in southeastern Pennsylvania and southwestern New Jersey, one county in northern Delaware and one county in northeastern Maryland. The MSA has a population of over 6 million, while the CSA has a population of over 7.1 million (as of the 2010 Census Bureau count). Philadelphia, being the region's major commercial, cultural, and industrial center, wields a rather large sphere of influence that affects the counties that immediately surround it.Some of the Delaware Valley's most well-known contributions to human civilization involve the region's higher education and medical institutions. The Delaware Valley has been influential upon American history and industry. The region are leaders in higher education, biotechnology, medicine, tourism and many others. With a gross domestic product of $388 billion, Philadelphia ranks ninth among world cities and fourth in the nation.
