Kansas ( /ˈkænzəs/ (help·info)) is a state located in the Midwestern United States.[4] It is named after the Kansas River which flows through it, which in turn was named after the Kansa tribe, who inhabited the area.[5] The tribe's name (natively kką:ze) is often said to mean "people of the wind" or "people of the south wind," although this was probably not the term's original meaning.[6][7] Residents of Kansas are called "Kansans." Historically, the area was home to large numbers of nomadic Native Americans who hunted bison. It was first settled by European Americans in the 1830s, but the pace of settlement accelerated in the 1850s, in the midst of political wars over the slavery issue. When officially opened to settlement by the U.S. government in 1854, abolitionist Free-Staters from New England and pro-slavery settlers from neighboring Missouri rushed to the territory to determine if 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 eventually prevailed and on January 29, 1861,[8][9] Kansas entered the Union as a free state. After the Civil War, the population of Kansas exploded when waves of immigrants turned the prairie into productive farmland. Today, Kansas is one of the most productive agricultural states, producing many crops, and leading the nation in wheat, sorghum[10] and sunflower production most years. Kansas is bordered by Nebraska on the north; Missouri on the east; Oklahoma on the south; and Colorado on the west. The state is divided into 105 counties with 628 cities, and is located equidistant from the Pacific and Atlantic oceans. The geographic center of the 48 contiguous states is located in Smith County near Lebanon. The geodetic center of North America was located in Osborne County until 1983. This spot was used until that date as the central reference point for all maps of North America produced by the U.S. government. The geographic center of Kansas is located in Barton County. Kansas is underlain by a sequence of horizontal to gently westward dipping sedimentary rocks. A sequence of Mississippian, Pennsylvanian and Permian rocks underlie the eastern and southern part of the state. The western half of the state consists of Cretacous through Tertiary sediments derived from the erosion of the uplifted Rocky Mountains to the west. The northeastern corner of the state was subjected to glaciation in the Pleistocene and is covered by glacial drift and loess. The western two-thirds of the state, lying in the great central plain of the United States, has a generally flat or undulating surface, while the eastern third has many hills and forests. The land gradually rises from east to west; its altitude ranges from 684 ft (208 m) along the Verdigris River at Coffeyville in Montgomery County, to 4,039 ft (1,231 m) at Mount Sunflower, one half mile from the Colorado border, in Wallace County. It is a popular belief that Kansas is the flattest state in the nation, reinforced by a well-known 2003 study[11] stating that Kansas was indeed "flatter than a pancake".[12] This has since been debunked, with most scientists ranking Kansas somewhere between 20th and 30th flattest state, depending on measurement method.[13] The Missouri River forms nearly 75 mi (121 km) of the state's northeastern boundary. The Kansas River (locally known as the Kaw), formed by the junction of the Smoky Hill and Republican rivers at appropriately-named Junction City, joins the Missouri at Kansas City, after a course of 170 mi (270 km) across the northeastern part of the state. The Arkansas River (pronunciation varies), rising in Colorado, flows with a bending course for nearly 500 mi (800 km) across the western and southern parts of the state. It forms, with its tributaries (the Little Arkansas, Ninnescah, Walnut, Cow Creek, Cimarron, Verdigris, and the Neosho), the southern drainage system of the state. Other important rivers are the Saline and Solomon Rivers, tributaries of the Smoky Hill River; the Big Blue, Delaware, and Wakarusa, which flow into the Kansas River; and the Marais des Cygnes, a tributary of the Missouri River. Areas under the protection of the National Park Service include:[14] Kansas contains three climate types, according to the Köppen climate classification: humid continental, semiarid steppe, and humid subtropical. The eastern two-thirds of the state has a humid continental climate, with cold winters and hot summers. Most of the precipitation falls in the summer and spring. The western third of the state has a semiarid steppe climate. Summers are hot, often very hot. Winters are cold in the northwest and cool to mild in the southwest. Also, the western region is semiarid, receiving an average of only about 16 inches (40 cm) of precipitation per year. Chinook winds in the winter can warm western Kansas all the way into the 80°F (25°C) range. The far south-central and southeastern reaches of the state have a humid subtropical climate, hot summers, mild winters and more precipitation than the rest of the state. Precipitation ranges from about 46 inches (1200 mm) annually in the southeast of the state, to about 16 inches (400 mm) in the southwest. Snowfall ranges from around 5 inches (130 mm) in the fringes of the south, to 35 inches (900 mm) in the far northwest. Frost-free days range from more than 200 days in the south, to 130 days in the northwest. Thus, Kansas is the 9th or 10th sunniest state in the country, depending on the source. Western Kansas is as sunny as parts of California and Arizona. In spite of the frequent sunshine throughout much of the state, the state is also vulnerable to strong thunderstorms, especially in the spring. Many of these storms become Supercell thunderstorms. These can spawn tornadoes, often of F3 strength or higher. According to statistics from the National Climatic Data Center, Kansas has reported more tornadoes (for the period 1 January 1950 through to 31 October 2006) than any state except for Texas - marginally even more than Oklahoma. It has also - along with Alabama - reported more F5 tornadoes than any other state. These are the most powerful of all tornadoes. Kansas averages over 50 tornadoes annually.[15] According to NOAA, the all time highest temperature recorded in Kansas is 121°F (49.4°C) on July 24, 1936, near Alton, and the all time low is -40°F (-40°C) on February 13, 1905, near Lebanon. Kansas' all time record high of 121°F (49.4°C) ties with North Dakota for the fifth-highest all-time record high recorded in a state, behind California (134°F/56.7°C), Arizona (128°F/53.3°C), Nevada (125°F/51.7°C), and New Mexico (122°F/50°C). For millennia, the land that is presently Kansas was inhabited by Native Americans. The first European to set foot in present-day Kansas was Francisco Vásquez de Coronado, who explored the area in 1541. In 1803, most of modern Kansas was secured by the United States as part of the Louisiana Purchase. From 1812 to 1821, this larger portion of Kansas was part of the Missouri Territory. The jurisdictional history of southwest Kansas, specifically the area west of the 103rd meridian and south of the Arkansas River, is more complicated. Prior to the Louisiana Purchase France and Spain had disputed jurisdiction over a wide area of North America, a small part of which included territory now in Southwest Kansas. With the Louisiana Purchase the United States assumed the position of France in that dispute. The Adams-Onis Treaty of 1819, negotiated between the American Secretary of State John Quincy Adams and the Spanish Foreign Minister Luis de Onis Gonzalez Vara, completely resolved at least that portion of the dispute which concerned these disputed lands, including what is now southwest Kansas. Under the Adams-Onis Treaty all of the territory in North America which earlier had been the subject of dispute between Spain and France was conceded to Spain by the United States. In turn, under the terms of the Adams-Onis Treaty Spain awarded Florida to the United States. The Florida which the United States received from Spain included not only the territory of the present State of Florida, but also a coastal strip now located in southern Alabama, southern Mississippi, and south-eastern Louisiana. When Mexico achieved independence from Spain in 1821, the area of what is now southwestern Kansas that had been ceded to Spain under the Adams-Onis Treaty fell under Mexican rule. It became a small part of the contemporaneous Mexican State of Coahila y Tejas. In 1836 a portion of Coahila y Tejas seceded from Mexico and became the Republic of Texas. Although Mexico was forced de facto to recognize the independence of the Republic of Texas in 1836, the western boundary of the Republic of Texas remained in dispute. A small portion of the area in dispute between Mexico and the Republic of Texas is now southwestern Kansas. Under the "Treaties of Velasco," signed by General Antonio de Santa Ana on behalf of Mexico, this disputed area was recognized as part of the Republic of Texas. However, Mexico did not ratify the "Treaties of Velasco" on the ground that at the time of signing Santa Ana was not the President. (Indeed, only the American government had ever referred to these documents, one public and one secret, as treaties, and then only 10 years later by President Polk when justifying war with Mexico.) The Republic of Texas was annexed to the United States and simultaneously admitted into the Union as the 28th State on December 29, 1845. The large area which the Treaties of Velasco recognized as being part of the Republic of Texas all remained within the State of Texas at this time. The admission of Texas into the American Union as a State resulted in the rupture of diplomatic relations between Mexico and the United States. The territorial dispute ultimately led to the Mexican-American War. The conclusion of that war was formalized on February 2, 1848 with the Treaty of Guadalupe Hidalgo. One provision of that treaty established the western boundary of Texas as being in accordance with the Treaties of Velasco. Thus, with the Treaty of Guadalupe Hidalgo Mexico was removed as a contender for the large territory under consideration, a small part of which is now Southeastern Kansas. The Treaty of Guadalupe Hidalgo also transferred a large area, which has become called the Mexican Cession of 1848 and includes present-day California, Nevada, and Utah, all of present-day Arizona except for a strip along the southern border, western New Mexico (except for a strip along the southern border), that portion of present-day Colorado that is west of the crest of the Rocky Mountains, and a part of present-day Wyoming, to the United States. The Mexican Cession is distinct and separate from the clarification of the boundaries of the former Republic of Texas. However, the fate of the area that became southwestern Kansas was not part of the Mexican Cession but was affected only by the resolution of the boundary between Mexico and the former Republic of Texas.)