Some of its tributaries rise in the mountains to the south, in the territory belonging to the republic of Mexico, but the Gila gathers the greater part of its waters from a great plateau on the northeast.
1895, J[ohn] W[esley] Powell, chapter I, in Canyons of the Colorado, Meadville, PA: Flood & Vincent; republished as The Exploration of the Colorado River and Its Canyons, New York: Dover, 1961, page 20