South Dakota is a state in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux Native American tribes, who compose a large portion of the population and historically dominated the territory. South Dakota is the 17th most expansive, but the 5th least populous and the 5th least densely populated of the 50 United States. Once the southern part of the Dakota Territory, South Dakota became a state on November 2, 1889, simultaneously with North Dakota. Pierre is the state capital and Sioux Falls, with a population of about 171,000, is South Dakota's largest city. 

South Dakota is bordered by the states of North Dakota (on the north), Minnesota (to the east), Iowa (to the southeast), Nebraska (on the south), Wyoming (on the west), and Montana (to the northwest). The state is bisected by the Missouri River, dividing South Dakota into two geographically and socially distinct halves, known to residents as "East River" and "West River". 

Eastern South Dakota is home to most of the state's population, and the area's fertile soil is used to grow a variety of crops. West of the Missouri, ranching is the predominant agricultural activity, and the economy is more dependent on tourism and defense spending. Most of the Native American reservations are in West River. The Black Hills, a group of low pine-covered mountains sacred to the Sioux, are in the southwest part of the state. Mount Rushmore, a major tourist destination, is there. South Dakota has a temperate continental climate, with four distinct seasons and precipitation ranging from moderate in the east to semi-arid in the west. The state's ecology features species typical of a North American grassland biome.
How does it rank as a state in terms of size?
South Dakota is the 17th most expansive