The Pike's Peak Gold Rush that began in 1859 brought an unprecedented number of people into the Colorado Territory. Among the earliest gold discoveries in Colorado were placer deposits near the headwaters of the Arkansas River in Oro city. In 1860, Cache Creek, a mining camp near Granite, became the first settlement of note with a population of about 300. By the following year, Granite, located on either side of the Arkansas river, exploded to a population of 3,000. The settlement included a three-mile stretch of river and extended two-miles up Cache Creek. In 1867 free quartz gold was discovered and a mill was built. In 1868 the county seat was moved to Granite from the neighboring town of Dayton near present-day Twin Lakes, no longer in existence.