Nebraska is a state that lies in both the Great Plains and the Midwestern United States. It is bordered by South Dakota to the north, Iowa to the east and Missouri to the southeast, both across the Missouri River, Kansas to the south, Colorado to the southwest and Wyoming to the west. It is the only triply landlocked U.S. state. Nebraska's area is just over 77,220 square miles (200,000 km2) with almost 1.9 million people. Its state capital is Lincoln, and its largest city is Omaha, which is on the Missouri River. Indigenous peoples including Omaha, Missouria, Ponca, Pawnee, Otoe, and various branches of the Lakota (Sioux) tribes lived in the region for thousands of years before European exploration. The state is crossed by many historic trails and was explored by the Lewis and Clark Expedition.