<p> 1803</p><p>The United States acquires the South Dakota region with the $15 Million Louisiana Purchase from France. 1804</p><p>Meriwether Lewis and William Clark travel through the South Dakota region. </p><p>1825 Teton Sioux sign a peace treaty with the United States. 1832</p><p>Fort Pierre is built as a trading post. </p><p>1857 Sioux Falls is established. </p><p>1858 Yankton Sioux sign away most of their land to the United States. </p><p>1861</p><p>Congress organizes the Dakota Territory. 1866 Red Cloud’s war begins. </p><p>1868 Laramie Treaty creates a Sioux reservation west of the river. </p><p>1872 Dakota Southern Railroad reaches South Dakota. 1874</p><p>General Custer discovers gold in the Black Hills. 1876</p><p>The Sioux War begins in South Dakota. 1885</p><p>South Dakota adopts the official seal. 1889</p><p>South Dakota becomes the 40th state on November 1. 1890</p><p>A massacre takes place at Wounded Knee. </p><p>1918 South Dakota grants voting rights to women. </p><p>1924 Meridian Bridge was built. This was the first bridge across the Missouri. 1927</p><p>Carving begins at Mount Rushmore. 1934 Indian Reorganization Act passes. </p><p>1939</p><p>Work begins on Crazy Horse Monument. 1941</p><p>USS South Dakota is highly decorated for its service in World War II. 1959 Belle Fourche is named the geographical center of the United States. </p><p>1992 Legislature adopts the state flag. </p>