The Missouri River heads in Montana, flows south through North and South Dakota, skirts the border between Nebraska and Iowa, and cuts the State of Missouri in half before it reaches its confluence with the Mississippi, north of St. Louis.
Three rivers, the Jefferson, the Gallatin, and the Madison coverge in the Missouri Headwaters State Park in Montana and form the Missouri River.
Fifteen dams break the Missouri into a series of lakes, including Lake Sharp near Pierre, South Dakota.
The Niobara River flows through the Sandhills of Nebraska and dumps sand behind the Gavins Point Dam, downstream of its confluence with the Missouri. So much sand that the river became shallow enough to support a stand of river grasses and a few cattails.
Walk out onto the point of the Edward and Pat Jones State Park in Missouri and you can see the Upper Mississippi bump into the roiling Missouri. Fly over the Confluence and you can see the two rivers flow side by side for several miles downstream, until the Muddy Missouri muddies the clear Mississippi.
Note: I have altered the images of the source in Photoshop. Ash from forest fires fell on the sensor of my digital camera when I made the photograph of the source of the river. Normally this is never a problem with that camera. I did alot of work in Photoshop to clean the sky of ash.