National Arkansas Day is observed worldwide every January 11 to celebrate Arkansas as the 25th state to join the United States. This day honors the state's rich history, which includes its original name derived from the Arkansas River and the Algonquian term for the Quapaw people. The state, known as The Natural State, has a heritage that includes early European exploration by figures such as Hernando de Soto and the establishment of Arkansas Post in 1686. Although Arkansas's initial application for statehood was rejected due to slavery issues, it was eventually admitted to the Union on June 15, 1836. National Arkansas Day is part of the National State Days project launched by National Day Calendar to celebrate the unique culture and spirit of each U.S. state, with Arkansas being honored in the order of its admission to the Union.