Late in the fall of 1999, Ft. Defiance, Ariz., became the first town in Navajo Nation to replace potholed asphalt streets with concrete. The project was so successful that several other towns in the reservation are following Ft. Defiance's example. Navajo Nation is the largest Indian reservation in the United States, covering more than 25,000 square miles and encompassing portions of Arizona, New Mexico, and Utah. The Navajo Housing Authority decided to switch from asphalt to concrete after hearing Ft. Defiance residents complain about all the potholes in their existing asphalt roadways. A key reason for NHA's decision was the good performance of concrete pavements installed 13 years earlier in other residential areas on the reservation. Although the pavements had cracked in many places, the wearing surfaces were intact.