other states that had refused to reapportion their state legislatures or retained rules based on geographic districts. In a series of cases in the 1960s during the height of related civil rights activities, the Warren Court invoked a one person, one vote principle, applying the Equal Protection Clause of the constitution and holding that states had to organize their legislatures by districts that held approximately equal populations, and that these had to be redefined as necessary after each decade's census. Following World War II in the 1940s, Arkansas began to diversify its economy and see prosperity. During the 1960s, the state became the base of the Walmart corporation, the world's largest company by revenue, headquartered in Bentonville. In the 21st century, Arkansas's economy is based on service industries, aircraft, poultry, steel, and tourism, along with important commodity crops of cotton, soybeans and rice. Arkansas's culture is observable in museums, theaters, novels, television shows, restaurants, and athletic venues across the state. Notable people from the state include politician and educational advocate William Fulbright; former president Bill Clinton, who also served as the 40th and 42nd governor of Arkansas; general Wesley Clark, former NATO Supreme Allied Commander; Walmart founder and magnate Sam Walton; singer-songwriters Johnny Cash, Charlie Rich, Jimmy Driftwood, and Glen Campbell; actor-filmmaker Billy Bob Thornton; poet C. D. Wright; physicist William L. McMillan, a pioneer in superconductor research; poet laureate Maya Angelou; Douglas MacArthur; musician Al Green; actor Alan Ladd; basketball player Scottie Pippen; singer Ne-Yo; Chelsea Clinton; actress Sheryl Underwood; and author John Grisham. Etymology The name Arkansas initially applied to the Arkansas River. It derives from a French term, Arcansas, their plural term for their transliteration of akansa, an Algonquian term for the Quapaw people. These were a Dhegiha Siouan-speaking people who settled in Arkansas around the 13th century. Akansa is likely also the root term for Kansas, which was named after the related Kaw people. The name has been pronounced and spelled in a variety of ways. In 1881, the state legislature defined the official pronunciation of Arkansas as having the final "s" be silent (as it would be in French). A dispute had arisen between the state's two senators over the pronunciation issue. One favored (), the other (). In 2007, the state legislature passed a non-binding resolution declaring that the possessive form of the state's name is Arkansas's, which the state government has increasingly followed.