The Floyd River rises in northwestern
O'Brien County near the town of
Sanborn and flows generally southwestwardly through
Sioux,
Plymouth and
Woodbury counties, past the towns of
Sheldon,
Hospers,
Alton,
Le Mars,
Merill, and
Hinton. At Merrill the Floyd collects its largest tributary, the
West Branch Floyd River, which is about 40 mi (65 km) long. The West Branch rises near
Boyden in northeastern Sioux County and flows generally southward into Plymouth County, past
Maurice and
Struble. The Floyd enters Woodbury County near the
Leeds neighborhood of Sioux City. The Floyd River has come out of its banks on several occasions, causing disastrous flooding in Sioux City in 1892 and 1953. The river has since been the focus of an intensive
flood control project. The Floyd's lower channel through Sioux City has been straightened,
channelized, lined with
riprap and banked by a high earthen
levee. The Floyd River is the site of frequent
fish kills caused by
runoff of massive amounts of animal waste from farm
feedlots into the river. ==Charles Floyd==