I visited in your area this past weekend for the first time and read the article in The Pioneer about the complex history of the valleys name. After reading this article, a name came to my mind that I wish to put into the mix.
The Columbia River is one of the most storied and powerful rivers in the world, and to have your area be the source for the river is significant.
You also have numerous great year- round recreational opportunities and great hot springs to relax in when you have finished the day.
Thus I would suggest the name Columbia Headwaters Recreation and Relaxation. I believe this captures your importance as the Columbias source as well as the other important tourism aspects of the area. It will draw tourists to an important geographical point and allow them to enjoy themselves while they are here.
If you decide to choose my suggestion as for you marketing, I will be glad to return from my home in Houston, Texas to unveil the sign.