Supai is a census-designated place (CDP) in Coconino County, Arizona, United States, within the Grand Canyon. As of the 1990 census, the CDP had a population of 423; the 2000 census erroneously recorded a population of 0. The capital of the Havasupai Indian Reservation, Supai is currently the only community in the United States where mail is still carried out by mules. It is also the most remote community in the lower 48 states, and the only way to get to it is to take a helicopter or to hike or ride a mule along the Havasupai Trail. Supai is eight miles (13 km) from the nearest road. There are no cars in the community.