US Dept of Commerce National Oceanic and Atmospheric Administration National Weather Service Missouri Basin, Pleasant Hill 1803 North 7 Highway Pleasant Hill, MO 64080-9421 It has been known that the Missouri is the longer of the two rivers since Lewis and Clark. MISSOURI RIVER, in the central and northwest central United States, is a major tributary of the Mississippi River and the longest river in the United States (2,466 miles). The Missouri River is the longest River in North America and is longer than the Wisconsin River. The Missouri River is the longest river in the United States of America.. National Weather Service Advanced Hydrologic Prediction Service (AHPS) The Wisconsin River is 430 miles long. The Missouri--Mississippi River system forms the United State's longest stream. It drains a watershed of approximately 580,000 square miles. According to the USGS, Missouri River stretches for 2,341 miles from source to mouth the river beats out the Mississippi River as the longest river in the US. On March 13, 1819, Long left Pittsburgh on the “Western Engineer,” one of four steamboats in the Yellowstone Expedition, charged with traveling up the Missouri … Once below the dams at Great Falls, the river runs free for the next two hundred miles before spilling into Fort Peck Lake and is where most multiday float trips occur. Father Jacques Marquette and Louis Jolliet reached the mouth of … Missouri River (Montana) The Missouri is the longest river in the United States, flowing more than 2,500 miles from its source on the eastern slope of the Rockies near Three Forks, Montana, to its confluence with the Mississippi River at St. Louis, Missouri. This article is an itinerary.. Missouri River. The longest river that flows entirely in Missouri is the Gasconade River. It is approximately 280 miles long and flows in the central and south-central Missouri. The Missouri River is 2,341 miles long. Understand [] The Missouri River is 2,341 miles long. Long, multiday floats on the upper portion of the Missouri River are difficult due to the many dams and reservoirs. The Wisconsin River is 430 miles long. The river originates from Ozarks and flows through several counties and Mark Twain National Park before emptying into the Missouri River. Floating Overview. The Missouri River is the longest River in North America and is longer than the Wisconsin River. The earliest commercial use of the river was during the fur trade. Unsettled Weather Continues in California & the Great Basin; Heavy Rain and Flooding Possible in Hawaii. Other Significant Rivers In Missouri. The river starts flowing from the Rocky Mountains in Western Montana and drains into the Mississippi River. It was the route of the Lewis and Clark expedition, Native Americans, fur traders, steamboats and railroads.. A large and slow-moving storm system will deliver locally heavy rain, possible flooding and heavy mountain snowfall to California and the Great Basin early this week.