Eagle Pass borders the city of Piedras Negras, Coahuila, Mexico, which is to the southwest and across the Rio Grande. The Eagle Pass-Piedras Negras Metropolitan Area (EG-PN) is one of six bi-national metropolitan areas along the United States-Mexican border. As of January 2008 (United States Census, 2008), the Eagle Pass Metropolitan Area's population is 48,401 people, and the Piedras Negras Metropolitan Area's population is 169,771. Eagle Pass was the first United States settlement on the Rio Grande. Originally known as Camp Eagle Pass, it served as a temporary outpost for the Texas militia, which had been ordered to stop illegal trade with Mexico during the Mexican-American War.