Leupp LOOP is a census-designated place in Coconino County, Arizona, on the Navajo Nation, United States. The population was 951 at the 2010 census. In 1902 an Indian boarding school was constructed here, administered by the Bureau of Indian Affairs. It had been closed before the US entry into World War II. In 1942 the facility was converted for use as the Leupp Isolation Center, designed to detain Japanese and Japanese-American internees from the several larger internment camps established by the War Relocation Authority to hold citizens and immigrants from the West Coast.