The basics: About 6 million years ago, the waterway now called the Colorado River began carving the geological wonder that is the Grand Canyon. The great expanse — now an icon of the national parks — averages 10 miles from the South Rim to the North Rim, and is 1 mile deep. In 1979, the Grand Canyon was designated a World Heritage Site.
Visitors: 5.52 million people visited the park in 2015.
Square miles: 1,904.
Established: 1919.
More information: nps.gov/grca; 1-928-638-7888.
