Where in the United States is the only place where the U.S. Mail is delivered by mule?

Supai, AZ, ZIP Code 86435, is the only place in the United States where mail delivery is carried out by mules.

Located within the Grand Canyon, Supai is only accessible by foot, pack animal or helicopter. Mail and package delivery to the community is thus delayed; delivery time for mail from Bullhead City, Arizona, via the United States Postal Service is at least a week because it is carried out by mule.

Supai (Havasupai: Havasuuw) is a census-designated place (CDP) in Coconino County, Arizona, United States.

As of the 2010 census, the CDP had a population of 208 and 43 households.

It is the capital of the Havasupai Indian Reservation.

The Havasupai Indians are instrumental in the management of the Grand Canyon along with the National Parks Department.

Supai has been referred to as "the most remote community" in the contiguous United States by the U.S. Department of Agriculture. It is accessible only by helicopter, on foot or by mule. Supai is 8 miles (13 km) from the nearest road and has no automobiles in the community, and can be reached by hiking 8 miles (13 km), descending 2,004 feet (611 m) in elevation from Hualapai Hilltop through the Hualapai Canyon.

Alternatively, the AirWest Helicopters service schedules flights from Hualapai Hilltop to Supai. Hualapai Hilltop is located about 70 miles (110 km) from the community of Peach Springs, AZ, along paved BIA Road 18.