The U.S. acquired the region as part of the Louisiana Purchase in 1803, and it was explored by Lewis and Clark in 1804–1806. Fort Pierre, the first permanent settlement, was established in 1817.
South Dakota shows some of the earliest geologic history of the continent in the rock formations of the ancient Black Hills and in the Badlands. In the area between the White River and the south fork of the Cheyenne, the Badlands display in their deeply eroded clay gullies not only colorful, fantastic shapes, but also a wealth of easily accessible marine and land fossils.
Agriculture is a cultural and economic mainstay, but it no longer leads the state in employment or share of gross state product. Durable-goods manufacturing and private services have evolved as the drivers of the economy. Tourism is also a booming industry in the state, generating over a billion dollars' worth of economic activity each year.
The Black Hills are the highest mountains east of the Rockies. Mt. Rushmore, in this group, is famous for the likenesses of Washington, Jefferson, Lincoln, and Theodore Roosevelt, which were carved in granite by Gutzon Borglum. A memorial to Crazy Horse is also being carved in granite near Custer.