The Grand Canyon is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. It encompasses 1,218.375 acres which represents 1,904 square miles. The Canyon was carved over a period of millions and millions of years by the Colorado River and therefore most people measure the size of the Grand Canyon by the length of the portion of the Colorado River from the eastern-most to western-most ends of the Canyon which is 277 miles long.