When Bulletin 478 was published by the United States Geological Survey, the big mines around Lake City, Colorado, had all been discovered and many had been worked for decades. Some of the more famous included the Golden Fleece, Ute-Ulay, Hidden Treasure, Pelican, Black Crooke, and the Golden Wonder. Many more mines had already been abandoned, believed to contain only low-grade ore. However, it was later discovered that rich ore in the Lake City area often lay in pockets surrounded, or hidden as some might say, by low-class deposits. As a result, the writings of John Duer Irving (who investigated the area in 1904) and the writings of Howland Bancroft (who was in the area in 1908) were combined and published in 1911. Both men were well-known and respected Colorado geologists of the time, who published many other works on San Juan mines. Lake City's mining was punctuated with boom and bust cycles up to that time; but much of the development of the local mines and in the local mining districts (the Lake and Galena Districts) is reported in this work, which also includes early maps, photographs, and production figures.