I want to let you know about a little tool we just recently added to our Game & Parks webpage. If you use the Missouri River for any kind of recreational activity, and that would be the Missouri River from one end of Nebraska to the other, you will want to spend some time exploring this:
We have an interactive map displaying all of the public access to the Missouri River. Here is the link, Missouri River Outdoor Recreation Access Guide.
Spend some time scrolling around exploring that map. I believe you will find it very helpful. It was not perfect, but certainly provides a resource for Missouri River boat ramps and access points that to my knowledge we have not had in one place before. Hope it helps you get out on the river and explore it, fish it!