Navajo Bridge crosses the Colorado River's Marble Canyon near Lee's Ferry in the US state of Arizona. Apart from the Glen Canyon Bridge a few miles upstream at Page, Arizona, it is the only roadway crossing of the river and the Grand Canyon for nearly 600 miles (970 km). Spanning Marble Canyon, the bridge carries northbound travelers to southern Utah and to the Arizona Strip, the otherwise inaccessible portion of Arizona north of the Colorado River, which includes the North Rim of Grand Canyon National Park.
Prior to the construction of the first Navajo Bridge, the only river crossing from Arizona to Utah was at nearby Lee's Ferry, where the canyon walls are low and getting vehicles onto the water is relatively convenient. The ferry offered only unreliable service, however, as adverse weather and flooding regularly prevented its operation. http://www.nps.gov/glca/historyculture/navajobridge.htm