436 mi (702 km) long, rises in Blue Ridge Mountains of n.e. Georgia, flows s.w. to West Point, Ga., and then s., forming Georgia-Alabama and Georgia-Florida boundaries; at Chattahoochee, Fla., joins Flint River to form the Apalachicola; navigable from Columbus, Ga., to mouth; inspired Sidney Lanier's poem, ‘The Song of the Chattahoochee'