Kansas ( (listen)) is a state in the Midwestern United States. Its capital is Topeka, its most populous county is Johnson County and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named after the Kansas River, which in turn was named after the Kansa Native Americans who lived along its banks. The tribe's name (natively kką:ze) is often said to mean "people of the (south) wind" although this was probably not the term's original meaning. For thousands of years, what is now Kansas was home to numerous and diverse Native American tribes. Tribes in the eastern part of the state generally lived in villages along the river valleys. Tribes in the western part of the state were semi-nomadic and hunted large herds of bison. The first Euro-American settlement in Kansas occurred in 1827 at Fort Leavenworth. The pace of settlement accelerated in the 1850s, in the midst of political wars over the slavery debate. When it was officially opened to settlement by the U.S. government in 1854 with the Kansas–Nebraska Act, abolitionist Free-Staters from New England and pro-slavery settlers from neighboring Missouri rushed to the territory to determine whether Kansas would become a free state or a slave state. Thus, the area was a hotbed of violence and chaos in its early days as these forces collided, and was known as Bleeding Kansas. The abolitionists prevailed, and on January 29, 1861, Kansas entered the Union as a free state, hence the unofficial nickname "The Free State". By 2015, Kansas was one of the most productive agricultural states, producing high yields of wheat, corn, sorghum, and soybeans. Kansas, which has an area of 82,278 square miles (213,100 square kilometers) is the 15th-largest state by area and is the 36th most-populous of the 50 states, with a population of 2,940,865 according to the 2020 census. Residents of Kansas are called Kansans. Mount Sunflower is Kansas's highest point at 4,039 feet (1,231 meters).