John Wesley Powell hired Cosmos and his brother Victor in 1881, when Powell was the director of the
Bureau of American Ethnology in Washington, D.C., to come west for the
Smithsonian Institution and survey the great pueblos of
Arizona and
New Mexico. After years of field-work, the Mindeleffs' field-party returned in 1888 to Washington, D.C., with their scientific findings, including many valuable archaeological artifacts. In 1890, Victor left the Smithsonian to pursue a career in architecture. In 1891, Cosmos came to Arizona to complete the stabilization of the
Casa Grande ruins until there was a shortage of money and the work was stopped. Cosmos left Casa Grande and began to research the extensive ruins found along the
Verde River instead. Accompanied by his wife Marion, Cosmos surveyed the river from its confluence with the
Salt River, north to the
Verde Valley and its confluence with
Beaver Creek. By the time he finished, he had catalogued more than 50 major sites. His study of the indigenous cultures of the Verde Valley was published in 1896. ==Later life==