Morrisville is a town in Wake County, North Carolina, United States. A small portion of the town extends into Durham County. Morrisville is part of the Research Triangle metropolitan region. The regional name originated after the 1959 creation of the Research Triangle Park, located midway between the cities of Raleigh and Durham. The Research Triangle region encompasses the U.S. Census Bureau's Combined Statistical Area (CSA) of Raleigh-Durham-Cary. The estimated population of the Raleigh-Durham-Cary CSA was 1,565,223 as of July 1, 2006, with the Raleigh-Cary Metropolitan Statistical Area (MSA) portion estimated at 994,551 residents. Morrisville is located in the northeast central region of North Carolina, where the North American Piedmont and Atlantic Coastal Plain regions meet. This area is known as the "fall line" because it marks the elevation inland at which waterfalls begin to appear in creeks and rivers. As a result, most of Morrisville features gently rolling hills that slope eastward toward the state's flat coastal plain. Its central Piedmont location situates the county about three hours west of Atlantic Beach, North Carolina, by car and four hours east of the Great Smoky Mountains of the Appalachian range. According to the United States Census Bureau, the town has a total area of 6.8 square miles (17.5 sq.km).