[1] 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 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.
He also reported from Russia during the Bolshevik Revolution and from Europe during World War I.