The Nenana River icefogger 8 years ago Nenana River The 140 mile long Nenana River forms the eastern boundary of Denali National Park. This tributary of the Tanana River, is a popular white water rafting destination. The Nenana begins as a Class I, but turns into a Class IV in the Nenana Gorge. Share this: Share on Facebook (Opens in new window) Facebook Share on Pinterest (Opens in new window) Pinterest Email a link to a friend (Opens in new window) Email