Lubbock's nickname is the "Hub City," which derives from it being the economic, education, and health care hub of a multi-county region commonly called the South Plains. The area is the largest contiguous cotton-growing region in the World and is heavily dependent on irrigation water drawn from the Ogallala Aquifer. Lubbock is a city in and the county seat of Lubbock County, Texas, United States. The city is located in the northwestern part of the state, a region known historically as the Llano Estacado, and the home of Texas Tech University and Lubbock Christian University. At the 2010 census, Lubbock had a population of 229,573, making it the 87th most populous city in the United States and the 11th most populous city in Texas. The city is the economic Center of the Lubbock metropolitan area, which had an estimated 2009 population of 276,659.