Black Hills

The Arikara arrived by AD 1500, followed by the Cheyenne, Crow, Kiowa and Arapaho. The Lakota (also known as Sioux) arrived from Minnesota in the 18th century and drove out the other tribes, who moved west.[11][12] They claimed the land, which they called Ȟe Sápa (Black Mountains). The mountains commonly became known as the Black Hills.

Gold miners in the Black Hills

Abandoned cabin near Dewey in the southern Black Hills

François and Louis de La Vérendrye probably traveled near the Black Hills in 1743.[13] Fur trappers and traders had some dealings with the Native Americans.

European Americans increasingly encroached on Lakota territory. In order to secure safe passage of settlers on the Oregon Trail, and to end intertribal warfare, the United States government proposed the Fort Laramie Treaty of 1868, which established the Great Sioux Reservation west of the Missouri River and acknowledged indigenous control of the Black Hills. The treaty protected the Black Hills "forever" from European-American settlement. Both the Sioux and Cheyenne also claimed rights to the land, saying that their cultures considered it the axis mundi, or sacred center of the world.

Although rumors of gold in the Black Hills had circulated for decades (see Thoen Stone and Pierre-Jean De Smet), confirmation of the deposits came first in 1874, when Brevet Major General George Armstrong Custer of the 7th US Cavalry led an expedition there and discovered gold in French Creek. An official announcement of gold was made by the newspaper reporters accompanying the expedition. The following year, the Newton-Jenney Party conducted the first detailed survey of the Black Hills. The surveyor for the party, Dr. Valentine McGillycuddy, became the first European American to ascend to the top of Black Elk Peak. This highest point in the Black Hills is 7,242 feet (2,207 m) above sea level.

During the 1875–1878 gold rush thousands of miners went to the Black Hills; in 1880, the area was the most densely populated part of the Dakota Territory. Three large towns developed in the Northern Hills: Deadwood, Central City, and Lead. Around these clustered groups of smaller gold camps, towns, and villages. Hill City and Custer City sprang up in the Southern Hills. Railroads were quickly constructed to the previously remote area. From 1880 onwards the gold mines yielded about $4,000,000 annually, and the silver mines about $3,000,000 annually.

Inyan Kara is a sacred mountain to the Lakota people

The conflict over control of the region sparked the Black Hills War (1876), also known as the Great Sioux War, the last major Indian War on the Great Plains. Following the defeat of the Lakota and their Cheyenne and Arapaho allies in 1876, the United States took control of the Black Hills. Despite their forced relocations, the Lakota never accepted the validity of the US appropriation. They have continued to try to reclaim the property,[14] and filed a suit against the federal government.

On July 23, 1980, in United States v. Sioux Nation of Indians, the Supreme Court of the United States ruled that the Black Hills were illegally taken by the federal government and ordered remuneration of the initial offering price plus interest, nearly $106 million. The Lakota refused the settlement, as they wanted the Black Hills returned to them. The money remains in an interest-bearing account, which, as of 2015, amounts to over $1.2 billion, but the Lakota still refuse to take the money. They believe that accepting the settlement would allow the US government to justify taking ownership of the Black Hills.

In 2012, United Nations Special Rapporteur James Anaya conducted a 12-day tour of Native Americans' land to determine how the U.S. is carrying out the United Nations Declaration on the Rights of Indigenous Peoples, endorsed in 2010 by the Obama administration. Anaya met with tribes in seven states on reservations and in urban areas as well as with members of the Obama administration and the Senate Committee on Indian Affairs. In an appeal issued August 21, 2012, Anaya brought a sale of over 1,900 acres of land in Black Hills by the Reynolds family to the attention of the U.S. government and asked that it disclose measures taken by federal or state governments to address Sioux concerns over the sale of the land within Reynolds Prairie. These acres consist of five land tracts, including the sacred Pe' Sla site for Dakota, Lakota, and Nakota peoples; natives to the Black Hills fundraised to buy the land during the Reynolds' sale.[15]

On January 15, 2013, the U.S. responded, telling Anaya that it "understands several tribes purchased the Pe' Sla sacred site around November 30, 2012" meaning the Pe' Sla is officially Sioux land.[16] After 2,022 acres of Pe' Sla (Reynolds Prairie) were granted Federal Indian trust status by the Bureau of Indian Affairs in March 2016, the Shakopee Mdewakanton tribe released a statement acknowledging the 2012 land purchase of 1,940 acres of Pe' Sla and also stated that this purchase was the result of a joint effort by the Rosebud, Shakopee Mdewakanton, Crow Creek, and Standing Rock Sioux Tribes.[17] In March 2017, Pennington County agreed to abandon its claim to the Pe' Sla area and recognize its Federal Indian trust status.[18] In 2016, the Southern Cheyenne and Arapaho Tribe of Oklahoma, the Northern Cheyenne Tribe of Montana and the Rosebud Sioux Tribe of South Dakota bought land near the sacred Bear Butte site for $1.1 million.[19] In 2018, the Northern Cheyenne Tribe of Montana and the Arapahoe Tribe of Oklahoma teamed together to purchase land near Bear Butte for $2.3 million.[20]

The granite core of the Black Hills rises 7,244 feet (2,208 m) at Black Elk Peak

The 'bull's eye' of this target is called the granite core. The granite of the Black Hills was emplaced by magma generated during the Trans-Hudson orogeny and contains abundant pegmatite. The core of the Black Hills has been dated to 1.8 billion years. Other localized deposits have been dated to around 2.2 to 2.8 billion years. One of these is located in the northern hills. It is called French Creek Granite although it has been metamorphosed into gneiss. The other is called the Bear Mountain complex, and it is located in the west-central part of the hills.

The angular unconformity between the Deadwood Formation and the underlying Precambrian rocks near Rapid City.

"Making a concentric ring around the core is the metamorphic zone. The rocks in this ring are all very old, as much as 2 billion years and older. This zone is very complex, filled with many diverse rock types. The rocks were originally sedimentary until there was a collision between the North American continent and a terrane. This collision, called the Trans-Hudson Orogeny, caused the original rocks to fold and twist into a vast mountain range. Over millions of years, these tilted rocks, which in many areas are tilted to 90 degrees or more, eroded. Today we see the evidence of this erosion in the Black Hills, where the metamorphic rocks end in an angular unconformity below the younger sedimentary layers.

The final layers of the Black Hills consist of sedimentary rocks. The oldest lie on top of the metamorphic layers at a much shallower angle. This rock called the Deadwood Formation is mostly sandstone and was the source of gold found in the Deadwood area. Above the Deadwood Formation lies the Englewood Formation and Pahasapa limestone, which is the source of the more than 200 caves found in the Black Hills, including Jewel Cave and Wind Cave. The Minnelusa Formation is next and is composed of highly variable sandstones and limestones followed by the Opeche shale and the Minnekahta limestone.

The next rock layer, the Spearfish Formation, forms a valley around the hills called the Red Valley and is often referred to as the Race Track.[21][22] It is mostly red shale with beds of gypsum, and circles much of the Black Hills. These shale and gypsum beds, as well as the nearby limestone beds of the Minnekahta, are used in the manufacture of cement at a cement plant in Rapid City. Next is the shale and sandstone Sundance Formation, which is topped by the Morrison Formation and the Unkpapa sandstone.

The outermost feature of the dome stands out as a hogback ridge. The ridge is made out of the Lakota Formation and the Fallriver sandstone, which are collectively called the Inyan Kara Group. Above this, the layers of rocks are less distinct and are all mainly grey shale with three exceptions: the Newcastle sandstone; the Greenhorn limestone, which contains many shark teeth fossils; and the Niobrara Formation, which is composed mainly of chalk. These outer ridges are called cuestas.

Fallingrock cliff in Dark Canyon. The rock is of Paleozoic age but is capped with a Cenozoic gravel terrace.

The preceding layers were deposited horizontally. All of them can be seen in core samples and well logs from the flattest parts of the Great Plains. It took a period of uplift to bring them to their present topographical levels in the Black Hills. This uplift called the Laramide orogeny, began around the beginning of the Cenozoic and left a line of igneous rocks through the northern hills superimposed on the rocks already discussed. This line extends from Bear Butte in the east to Devils Tower in the west. Evidence of Cenozoic volcanic eruptions, if this happened, has long since been eroded.

The Black Hills also has a 'skirt' of gravel covering them in areas, which are called pediments. Formed as the waterways cut down into the uplifting hills, they represent the former locations of today's rivers. These beds are generally around 10,000 years old or younger, judging by the artifacts and fossils found. A few places, mainly in the high elevations, are older, as old as 20 million years, according to camel and rodent fossils found. Some gravels have been found but for the most part, these older beds have been eroded.