Hagerstown is a city in northwestern Maryland, United States. It is the county seat of Washington County, and, by many definitions, the largest city in a region known as Western Maryland. The population of Hagerstown city proper, according to estimates conducted by the United States Census Bureau for a 12-month period ending 1 July 2008, is 39,728, and the total 2000 Urbanized Area population is 120,326 (~80,000 in MD). Hagerstown ranks as Maryland's sixth largest city, but if the urban area were to likewise incorporate, it would be Maryland's second-most populous city. Hagerstown anchors the Hagerstown-Martinsburg, MD-WV Metropolitan Statistical Area, which lies just northwest of the Washington-Baltimore-Northern Virginia, DC-MD-VA-WV Combined Statistical Area in the heart of the Great Appalachian Valley. The population of the metropolitan area in 2000 was 222,771 and the 2008 estimate is 263,753 (U.S. Rank 169). Greater Hagerstown is the fastest growing metropolitan area in the state of Maryland and among the fastest growing in the United States. Despite its semi-rural Western Maryland setting, Hagerstown is a center of transit and commerce. Interstates 81 and 70, CSX, Norfolk Southern, and the Winchester and Western railroads, and Hagerstown Regional Airport form an extensive transportation network for the city. Hagerstown is also the chief commercial and industrial hub for a greater Tri-State Area that includes much of Western Maryland as well as significant portions of South Central Pennsylvania and the Eastern Panhandle of West Virginia. Hagerstown has often been referred to as, and is nicknamed, the Hub City.