The Choctaw people are descendants of the Hopewell and Mississippian cultures, who lived throughout the east of the Mississippi River valley and its tributaries. About 1,700 years ago, the Hopewell people built Nanih Waiya, a great earthwork mound located in what is central present-day Mississippi. It is still considered sacred by the Choctaw. The early Spanish explorers of the mid-16th century in the Southeast encountered Mississippian-culture villages and chiefs. The anthropologist John R. Swanton suggested that the Choctaw derived their name from an early leader. Henry Halbert, a historian, suggests that their name is derived from the Choctaw phrase "Hacha hatak" (river people).