The mines were owned by the Anglo American U.B. Teader mining company in 1867. They later sold them to the Moctezuma Copper Co., which part of the Phelps Dodge company. American-style houses were built. A library and a small hospital were also built. When the mines were opened, copper was carried by mules. In 1904 the railroad was built, so the copper was moved by train. By 1907, Nacozari had become the metropolis of far northeastern Sonora. The population was 5,000 people, mostly Mexicans and Americans, with some Chinese people. Phelps kept the mines until 1948 when the copper had all been taken out.