Which river flows through the Grand Canyon?

The Colorado carved the Grand Canyon, and the mechanism matters more than the name. The river itself did not simply dig downward on its own; the whole Colorado Plateau was slowly uplifted while the river held its course, so it sawed through rising rock like a wire through cheese. Because the layers exposed in the walls are nearly horizontal and were laid down over an immense span of time, the canyon is one of the clearest cross-sections of Earth's history anywhere accessible, with ancient basement rock at the bottom of the inner gorge and much younger sedimentary beds at the rim. Side canyons, flash floods and freeze-thaw weathering did the widening that the river alone could never accomplish. Downstream the Colorado is so heavily dammed and diverted for cities and irrigation across the American Southwest that in many years little or none of it reaches the sea in Mexico.

The Glen Canyon Dam upstream traps sediment and steadies temperatures, which has changed the river's beaches and native fish inside the canyon.