Key events in the 20th century included the Dust Bowl and Great Depression, increased federal spending during the 1940s and 1950s for agriculture and defense, and an industrialization of agriculture that has reduced family farming. While several Democrats have represented South Dakota for multiple terms in both chambers of Congress, the state government is largely controlled by the Republican Party, whose nominees have carried South Dakota in each of the last 13 presidential elections. Historically dominated by an agricultural economy and a rural lifestyle, South Dakota has recently sought to diversify its economy in other areas to both attract and retain residents. South Dakota's history and rural character still strongly influence the state's culture. History Humans have lived in what is today South Dakota for several thousand years. The first inhabitants were Paleoindian hunter-gatherers, and disappeared from the area around 5000 BC. Between 500 AD and 800 AD, a semi-nomadic people known as the Mound Builders lived in central and eastern South Dakota. In the 14th century, the Crow Creek Massacre occurred, in which several hundred men, women, and children were killed near the Missouri River. By 1500, the Arikara (or Ree) had settled in much of the Missouri River valley. European contact with the area began in 1743, when the LaVérendrye brothers explored the region. The LaVérendrye group buried a plate near the site of modern-day Pierre, claiming the region for France as part of greater Louisiana. In 1762 the entire region became part of the Spanish Louisiana until 1802. By the early 19th century, the Sioux had largely replaced the Arikara as the dominant group in the area. In 1803, the United States purchased the Louisiana Territory, an area that included most of South Dakota, from Napoleon Bonaparte, and President Thomas Jefferson organized the Lewis and Clark Expedition to explore the region. In 1817, an American fur trading post was set up at present-day Fort Pierre, beginning continuous American settlement of the area. In 1855, the U.S. Army bought Fort Pierre but abandoned it in 1857 in favor of Fort Randall to the south. Settlement by Americans and Europeans was by this time increasing rapidly, and in 1858 the Yankton Sioux signed the 1858 Treaty, ceding most of present-day eastern South Dakota to the United States. Land speculators founded two of eastern South Dakota's largest present-day cities: Sioux Falls in 1856 and Yankton in 1859. In 1861, the