East River (South Dakota)

Geographical distinctions between the eastern and western sections of the state were reinforced by differing patterns of European-American settlement and Native American resettlement during the 19th and 20th centuries.

The eastern half of South Dakota was heavily glaciated and is largely covered by glacial till and loamy soil, which has lent itself to agricultural uses.

During the second half of the 19th century, about 350,000 immigrants from western and northern Europe settled to the east of the Missouri.

The later European immigrants, however, predominantly from southern and eastern Europe, settled in the West River region after 1889, when the federal government made some 9 million acres of former Lakota land available for purchase after breaking up the Great Sioux Reservation, established under the Fort Laramie Treaty of 1868.

About 70% of South Dakota's population in the 1990s was located in the East River region, which includes major businesses, industries and state government.