The region's population grew steadily after the Union Pacific Railroad reached the town of Cheyenne in 1867, and the federal government established the Wyoming Territory on July 25, 1868. Wyoming lacked significant deposits of gold and silver, unlike mineral-rich Colorado, and did not experience Colorado's related population boom. However, South Pass City did have a short-lived boom after the Carissa Mine began producing gold in 1867. Furthermore, copper was mined in some areas between the Sierra Madre Mountains and the Snowy Range near Grand Encampment.