Gold can be found in small quantities almost everywhere in the world, but it is especially concentrated in geologic regions affected by ancient episodes of mountain building. These events created cracks in the earth's crust; mineral rich solutions seeped upward through these fissures and deposited their valuable cargo in rock layers near the surface. This is why the famous gold rushes that swept the western United States usually occurred in areas known for their high and rugged mountain ranges, such as California, Colorado, and Alaska. The Black Hills of South Dakota are neither as high nor as rugged as the Rocky Mountains or the Sierra Nevada, but they are the remains of a very old mountain range, much older in fact than the mountains of Colorado and California. And they are rich in gold and other precious and useful metals.

The gold rush that struck the Black Hills of South Dakota in the 1870s is an integral part of the struggle for control of the northern Great Plains between the Indian nations who lived and hunted buffalo there and Euro-American intruders from the east-miners, railroad-builders, ranchers, and farmers. Sacred to the Indians, the Black Hills themselves were the center of a large area reserved to the Sioux (Lakota) and Cheyenne by the Treaty of Fort Laramie (1868). The rumored presence of gold in the Black Hills, however, proved a powerful incentive for new white incursions in the area. An expedition led by Lt. Col. George A. Custer in the summer of 1874 confirmed the rumors of gold, and by October of that year the first party of gold-seekers had arrived in the region. At first, the U.S. Army attempted to prevent these violations of the 1868 treaty, but in the fall of 1875 it gave up its objections and prospectors poured into the region. In 1876, the richest gold fields in the region were soon found to be those straddling the narrow gulches in the vicinity of the modern cities of Deadwood and Lead. Lead-now the largest city in the region-appears on our core map as "Lead City." Deadwood lies a few miles to the north off the left margin of the map, although Deadwood Gulch, the center of attention in the early years of the rush in this district, may be found prominently on the map. The famous "Homestake" claim and others near Lead were established in 1876. The Homestake Mining Company formally began operations in 1877. Under the shrewd guidance of financier George Hearst the Homestake Company soon became the dominant mining operation in the area. By the early 1880s it had absorbed most of the rival claims, including that of the Caledonia Mining Co. The enlarged Homestake mine continues in operation today as the largest gold mine in the United States.

Our core map was published as a supplement to a series of reports by mining engineers for the Caledonia Mining Company, whose operations were located less than a mile from the Homestake mine and Lead City. The reports were published in 1879, when the mining company was still an independent operation. Note that most of the claims marked on the map are rectangular, roughly 200-300 feet by 1000-1500 feet. The size of initial claims in mining districts was usually limited by locally determined regulations. Even so, a few claims overlapped with each other, leading to conflicts that had to be resolved by negotiation. The claims were typically rectangular, as this shape allowed miners to tunnel some distance into mountainsides to follow veins of gold-bearing ore (usually quartzite), which were themselves usually linear in shape. From the map it is plain to see that the exceedingly rich lode miners were pursuing in this area ran roughly northwest (at the lower left of the map) to the southeast (at the upper right). (Note that the north arrow points off the upper left corner of the map.) When the map was printed in 1879, the consolidation of the many claims in the area, which would culminate in the dominance of the Homestake Mining Company, had already begun. Consolidated claims are outlined with hachures. For example the Caledonia Mining Company's claims includes the original Caledonia claim as well as the adjacent Queen of the Hills and Grand Prize claims.

Note that the claims were often named after people, perhaps including the original claimants, their family members, and famous people. Others, such as "Golden Prospect" and "Grand Prize," expressed the claimants' high hopes for their little patches of mountainside. A "homestake" was a claim thought to be rich enough to send a prospector home satisfied and wealthy. The summits of the steep hills that line the various gulches and creeks in this area are indicated by hachures that snake across the map like large caterpillars. Several mill sights are also located on the map. The mills (called stamp mills) relied on water power to pulverize the gold-bearing ore, thus making it possible to sift out and purify the gold from the quartzite ore that contained it.

Here as elsewhere most of the early gold discoveries were made by placer mining-that is by sifting through the silt, mud, and sand of a stream bed for bits of gold washed from an adjacent mountainside containing gold-bearing ores. Placer mining was a major source of wealth in the gold fields of California, Colorado, and Alaska, but was less successful here, and gave way quickly to the other main forms of mining, open pit (open cut, or surface) mining and underground (shaft, or stope) mining.

The core map includes two diagrams (below the map and at upper right) that, with careful reading, allow us to gain a three-dimensional understanding of the operations of the Caledonia mine. Below the map is a longtitudinal (or vertical) section of the mine showing us the location of tunnels, mineshafts, and gold ore veins as if half of the hillside has been torn away to allow us to view them. At upper right is a horizontal section (with East at the top) viewing the mine from above as if the top of the hill has been sliced off down to the level of the Grand Prize Tunnel. Note that while the longitudinal sections gives us the impression that the Lower (or Caledonia) Tunnel lies directly below the Grand Prize Tunnel, the horizontal section shows that it is offset slightly to the north and at an angle of about 10º to the east. The surface entrances of both tunnels are to the west (off the bottom edge of the horizontal section). The location of three veins or lodes of gold rich ore (the smaller Discovery and Blind Lodes, and the larger and richer "Main" Lode-as it is called in the accompanying report) are marked on the horizontal section by stippling. On the longitudinal section, the Main Load is not stippled, but covers the entire right half of the section marked "Reserves."

The accompanying report by the superintendent of the mine, J.H. Rigby, tells us that the owners of the original, smaller, Caledonia claim bought the adjacent Queen of the Hills and Grand Prize claims because these offered a better access to the lode of gold ore they were seeking. Initially ore was extracted from the hillside by a surface mine (marked as "open cut" on the longitudinal section and as "upper workings" on the horizontal section). Next, two tunnels were begun that would provide access to the lode well below the surface of the hillside. The chief advantage of such tunnels compared to more vertical mineshafts or winzes is that they allow ore to be transported out of the mine by means of narrow-gauge railroads. The waste generated by the excavation of the tunnels may be seen on the longitudinal section, on the hillsides just below the tunnel entrances. Meanwhile, a winze (an inclined passageway) was constructed to connect the old surface mine with the Grand Prize Tunnel at the point where the tunnel reached the Main Lode. Winzes could also be used to transport ore (and miners) in and out of the mine, but also helped improve the quality of the air the miners breathed. Both diagrams show a prominent chamber, marked "stopes," where the richest veins of gold ore were currently being mined. Ore was exacavated from the ceiling of this chamber in layers called stopes. Under Rigby's direction, however, this method of mining was abandoned; instead, the chamber was expanded by means of smaller tunnels following the richest veins of ore within the lode. Two of these smaller tunnels are discussed in Rigby's report and may be seen reaching southward from the main mine chamber on the horizontal section.

We are not certain whether the original Caledonia mine is still in operation. The Homestake Mining Company is, however, very much alive. In 2001 it merged with Barrick Gold Corporation, forming the largest gold mining company in the world. The Homestake Mine itself is still the largest and most productive mine in the United States. Most of the other mines in the Black Hills have long since closed as the veins were exhausted or became too costly to work profitably. As mining operations slowed down in the early twentieth century, the Black Hills made a transition to a tourist resort, for which it is best known today. Some of this tourism celebrates the legacy of the region's mining history. Deadwood, for example, still holds an annual festival commemorating the golden days of 1876.