By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
San Juan County is in the western San Juan Mountains in southwestern Colorado, just south of Ouray County.
The county produced about 1,665,000 ounces of gold through 1959 and large quantities of silver, lead, copper, and zinc. The bulk of the gold came from lodes in the Animas (Silverton) and Eureka districts. There are no extensive placer deposits in the county.
Some prospecting in the county was carried on in the 1860's, and the first gold ore was mined in 1870 while the region was still part of the Ute Indian Reservation. The main rush to the region did not begin until 1874, after a treaty with the Ute Indians opened the region to settlement (Ransome, 1901b, p. 19-20). About 2,000 men came into the district during the summer of 1874, and at least that many claims were staked. San Juan County was formed in 1876 with the county seat at Silverton.
During the 1870's, the chief route into the region was by trail from Del Norte 125 miles away on the Rio Grande River and transportation was by pack train and wagon. Both transportation and ore treatment charges were high; consequently, only rich ore could be mined. The area, nevertheless, was actively prospected, and many lodes which subsequently proved valuable were located. In July 1882, the Denver and Rio Grande narrow-gage railroad was completed to Silverton, which reduced transportation rates and permitted the mining of lower grade ores. There followed a brief but turbulent period marked by unscrupulous promoting, squandering of large sums of money on fruitless mining ventures, and repeated failures to treat successfully the complex San Juan ores (Ransome, 1901b, p. 21-24). In 1890, treatment of low-grade ores by concentration and amalgamation at the Sunnyside and Silver Lake mines near Silverton started a new period in mine development. The first large-scale selective flotation mill, which successfully separated lead and zinc from ores from the Sunnyside mine, began operation in 1917-18 (W. S. Burbank, in Vanderwilt and others, 1947, p. 403).
Silver and lead ores were mined almost continuously in San Juan County from 1873 through 1923 (Henderson, 1926, p. 216). Gold production, which began in 1873, increased steadily, and with few exceptions after 1894 the value of gold produced exceeded that of silver. Profitable operations continued until 1953, when the Shenandoah-Dives mill near Silverton closed. The metal output of the county was small from 1953 through 1959.
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