Albuquerque (is the largest city in the state of New Mexico, United States. It is the county seat of Bernalillo County and is situated in the central part of the state, straddling the Rio Grande. The city population was 521,999 as of July 1, 2008, according to U.S. census estimates, and ranks as the 34th-largest city in the U.S. As of June 2007, the city was the 6th fastest growing in America. With a metropolitan population of 845,913 as of July 1, 2008, Albuquerque is the 59th-largest United States metropolitan area. The Albuquerque MSA population includes the city of Rio Rancho, one of the fastest growing cities in the United States. Roughly half of the population of the state of New Mexico lives in the Albuquerque area. Albuquerque is home to the University of New Mexico, Kirtland Air Force Base, Sandia National Laboratories, Lovelace Respiratory Research Institute, and Petroglyph National Monument. The Sandia Mountains run along the eastern side of Albuquerque, and the Rio Grande flows through the city, north to south.