 By discharge , the Missouri is the ninth largest river of the United States , after the Mississippi , St. Lawrence , Ohio , Columbia , Niagara , Yukon , Detroit , and St. Clair . The latter two , however , are sometimes considered part of a <unk> between Lake Huron and Lake Erie . Among rivers of North America as a whole , the Missouri is thirteenth largest , after the Mississippi , Mackenzie , St. Lawrence , Ohio , Columbia , Niagara , Yukon , Detroit , St. Clair , Fraser , Slave , and <unk> . 
