Kansas QuickInfo Est. Pop.: 2,694,511 Capital: Topeka Statehood: 1861 Nickname: Sunflower State Motto: Ad astra per aspera Official Website Census Info Fun KS Factoid The Arkansas River may be the only river whose pronunciation changes as it crosses state lines. In Kansas, it is called the Arkansas (ahr-KAN-zuhs). On both sides of Kansas (Colorado and Oklahoma), it is called the Arkansaw.