San Juan County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 705, making it the least populous county in Colorado. The county seat and the only incorporated municipality in the county is Silverton. The county name is the Spanish language name for "Saint John", the name Spanish explorers gave to a river and the mountain range in the area. With a mean elevation of 11,240 feet, San Juan County is the highest county in the United States and also has the two highest elevation houses in the United States; the ‘Bonnie Belle’ above Animas Forks at 11,900’ – 11,950’ elevation and an unnamed house above Picayune Gulch at 12,000’ elevation.

Silverton is a statutory town that is the county seat, the most populous community, and the only incorporated municipality in San Juan County, Colorado, United States. The town is located in a remote part of the western San Juan Mountains, a range of the Rocky Mountains. The first mining claims were made in mountains above the Silverton in 1860, near the end of the Colorado Gold Rush and when the land was still controlled by the Utes. Silverton was established shortly after the Utes ceded the region in the 1873 Brunot Agreement, and the town boomed from silver mining until the Panic of 1893 led to a collapse of the silver market, and boomed again from gold mining until the recession caused by the Panic of 1907. The entire town is included as a federally designated National Historic Landmark District, the Silverton Historic District.