<P> Name pronunciation varies by region . Many people in western states, including Kansas and parts of Colorado, pronounce it / ɑːr ˈkænzəs / ar - KAN - zəs, People in Oklahoma, Arkansas, parts of Colorado, and the majority of the remaining United States typically pronounce it / ˈɑːrkənsɔː / AR - kən - saw, which is how the Arkansas state is always pronounced according to a state law passed in 1881 . </P> <P> The path of the Arkansas River has changed over time . Sediments from the river found in a palaeochannel next to Nolan, a site in the Tensas Basin, show that part of the river's meander belt flowed through up to 5200 BP . Whilst it was previously thought that this relict channel was active at the same time as another relict of Mississippi River's meander belt, it has been shown that this channel of the Arkansas was inactive approximately 400 years before the Mississippi channel was active . </P> <P> The Arkansas has three distinct sections in its long path through central North America . At its headwaters beginning near Leadville, Colorado, the Arkansas runs as a steep fast - flowing mountain river through the Rockies in its narrow valley, dropping 4,600 feet (1.4 km) in 120 miles (193 km). This section supports extensive whitewater rafting, including The Numbers (near Granite, Colorado), Brown's Canyon, and the Royal Gorge . </P> <P> At Cañon City, Colorado, the Arkansas River valley widens and flattens markedly . Just west of Pueblo, Colorado, the river enters the Great Plains . Through the rest of Colorado, Kansas, and much of Oklahoma, it is a typical Great Plains riverway, with wide, shallow banks subject to seasonal flooding and periods of dwindling flow . Tributaries include the Cimarron River and the Salt Fork Arkansas River . </P>

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