The Gila River and its headwater tributaries - the East, West and Middle Forks - merge to become the dominant river of the region. It eventually flows out of New Mexico on its 649-mile journey to the Colorado River near Yuma, Arizona. This river has been named one of America’s most endangered. The Greater Gila Bioregion’s rivers, such as the San Francisco, the Blue and their tributaries are largely undammed and free flowing, a rare circumstance in the West. However, the threat of damming or massive diversion of the Gila moved closer in 2004 when Congress approved the Arizona Water Settlements Act. The Act settled claims with several Indian tribes and affirmed New Mexico's right to take about 14,000 acre-feet of water from the Gila and its tributary, the San Francisco. The Gila River served as a part of the border between the United States and Mexico after the Treaty of Guadalupe-Hidalgo in 1848 until the Gadsden Purchase of 1853 extended American territory south of the Gila.