Raleigh is the capital city and the second largest city in the state of North Carolina as well as the seat of Wake County. Raleigh is known as the "City of Oaks" for its many oak trees. According to the U.S. Census Bureau, the city's estimated population on November 22, 2010 was 426,708, over an area of 142.8 square miles, making Raleigh currently the 45th largest city in the United States. It is also one of the fastest growing cities in the country. The city of Raleigh is named after Sir Walter Raleigh. Raleigh, Durham, and Chapel Hill make up the three historically primary cities of the Research Triangle metropolitan region. The regional nickname of "The Triangle" originated after the 1959 creation of the Research Triangle Park, primarily located in Durham County, four miles from Downtown Durham and encompassed on three sides by the city of Durham and roughly midway between the cities of Raleigh and Chapel Hill and the three major research universities of NC State University, Duke University, and UNC-Chapel Hill.