Rio Grande , in Mexico Río Bravo, River, North America. One of the longest rivers of North America, it flows 1,900 mi (3,060 km) from its sources in the Rocky Mountains of southwestern Colorado, U.S., to the Gulf of Mexico. It rises high in the San Juan Mountains and flows generally south, passing southeast and forming the entire border between Texas and Mexico. The earliest European settlements were along the lower course of the river in the 16th century, but many of the Pueblo Indian settlements of New Mexico date from before the Spanish conquest. During the Spanish period, the middle and upper portions were called the Río del Norte, and the lower course was called the Río Bravo. It is a major source of irrigation. At the U.S.-Mexican border, it defines the edge of Big Bend National Park, Texas.
