Rio Grande Geography The Rio Grande is either the fourth or fifth longest river system in North America. It all depends on how it is measured. Because the river twists so much, it occasionally changes course. And these course shifts can cause it to be longer or shorter. At its last official measure, the Rio Grande clocked in at 1,896 miles. The river starts in Colorado and extends downward to the Gulf of Mexico. Downward is the best way of describing it too. Not only does the river extend south, but it also starts in the mountains and gets lower and lower in elevation as it extends to the Gulf. Its name is Spanish for the “Big River,” but the Rio Grande is actually known as Rio Bravo in Mexico. “Bravo” translates as “furious,” so the name makes sense. Because of its twists and turns, it certainly does seem to be angrier than most rivers!