A year ago I got some good advice on this forum when I asked about paddling up the Missouri. Thanks!
In 2016 I hiked and paddled the Lewis and Clark Trail from the Mississippi in Illinois, up the Missouri River, over the Rockies, then down the Clearwater, Snake and Columbia Rivers to the Pacific.
I hiked the first 800 miles of the Missouri, then paddled upstream the next 1,500 miles. It took nearly six months to cover the whole 3,300 miles.