The Rio Grande (/ˈriːoʊ ˈɡrænd/; Spanish: Río Bravo del Norte or Río Bravo, [ˈri.o ˈβra.βo]) is a river that flows from southwestern Colorado in the United States to the Gulf of Mexico. Along the way it forms part of the Mexico–United States border. According to the International Boundary and Water Commission, its total length was 1,896 miles (3,051 km) in the late 1980s, though course shifts occasionally result in length changes. Depending on how it is measured, the Rio Grande is the fourth or fifth longest river system in North America.