El Paso is the seat of El Paso County in the U.S. state of Texas an part of the American Southwest. According to the 2006 U.S. Census population estimates, the city had a population of 609,415. It is the sixth-largest city in Texas and the 21st-largest city in the United States, as well as the 7th fastest growing large city in the nation from 2000-2006. Its metropolitan area covers all of El Paso County, a portion of Hudspeth County and part of southern Doña Ana County, New Mexico. The metropolitan area has a population of 736,310.