The Osage is formed in southwestern Missouri, approximately 14 miles (23 km) northeast of Nevada on the Bates-Vernon County line, by the confluence of the Marais des Cygnes and Little Osage Rivers; the Marais des Cygnes is sometimes counted as part of the river, placing its headwaters in eastern Kansas and bringing its total length to over 500 miles (800 km).The river is named for the Osage Nation,[3] the historic indigenous people who dominated this region at the time when the first European settlers arrived.The river presented significant navigation difficulties for early settlers because of its fluctuating water levels, as well as the presence of shallow pools and sand bars caused by its tight meandering course through the hills.These changes made the lower reaches of the river navigable for steamboat commerce for a period of six to nine months out of the year.[4] In the 20th century, private construction of the Bagnell Dam, primarily to generate hydroelectricity, began in 1922 and was completed after nine years.