Where is the widest canyon?

Grand Canyon
   The Grand Canyon in Arizona is the widest canyon, 18 miles from rim to rim at its widest point. This chasm, up to 6,000 feet deep and 217 miles long, was carved by the Colorado River, beginning about 1 million years ago.
   Within the canyon are four different climate zones, each with a typical plant and animal life. The exposed, multicolored rocks reveal the early geologic history of the North American continent in nine separate, well-preserved, and readily visible layers, the formation of which dates back half a billion years. Pictographs from ancient cultures are visible on the canyon walls. Old adobe houses indicate inhabitation by Pueblo Indians as early as 1200.
   Much of the Grand Canyon was established as a national park in 1919. Areas added in 1975 doubled its size. Each year, 5 million people visit the canyon.