Harrisburg is located at (40.269789, -76.875613). According to the United States Census Bureau, the city has a total area of 29.6 km sq (11.4 square miles). 21.0 km sq (8.1 mi sq) of it is land and 8.6 km sq (3.3 mi sq) of it (29.11%) is water. Harrisburg is located in the Susquehanna Valley, a rich and fertile agricultural region in south-central Pennsylvania. The region is also situated at the extreme western fringe of the BosWash megalopolis, the name for a group of metropolitan areas in the northeastern United States. Directly to the north of Harrisburg lies the Blue Ridge MountainsBlue Ridge chain of the Appalachian Mountains. The Cumberland Valley lies directly to the west of Harrisburg and the Susquehanna River, stretching into northern Maryland. Harrisburg's western boundary is formed by the Susquehanna River, which also serves as the boundary between Dauphin County, PennsylvaniaDauphin and Cumberland County, PennsylvaniaCumberland counties. The city is divided into numerous neighborhoods and districts. Like many of Pennsylvania's cities and boroughs that are at "build-out" stage, there are several townships outside of Harrisburg city limits that, although autonomous, use the name ''Harrisburg'' for postal and name-place designation. They include the townships of: Lower Paxton Township, PennsylvaniaLower Paxton, Middle Paxton Township, PennsylvaniaMiddle Paxton, Susquehanna Township, Dauphin County, PennsylvaniaSusquehanna, Swatara Township, Dauphin County, PennsylvaniaSwatara and West Hanover Township, PennsylvaniaWest Hanover in Dauphin County. The borough of Penbrook, PennsylvaniaPenbrook, located just east of Reservoir Park (Harrisburg)Reservoir Park, was previously known as East Harrisburg. Penbrook, along with the borough of Paxtang, PennsylvaniaPaxtang, also located just outside of the city limits, maintain Harrisburg zip codes as well. The United States Postal Service designates 26 zip codes for Harrisburg, including 13 for official use by federal and state government agencies.{{cite web url Source: http://en.wikipedia.org/wiki/Harrisburg%2C_Pennsylvania