Here is a description of the Selway River in northern Idaho,
with almost 20 pictures:

http://cacreeks.com/selway.htm

Are Selway permits the hardest (least likely) to obtain?
I can't think of any other rivers quite like that, although
the Grand Canyon has a long waising list.

By the way, the creekin.net website has changed domain names.
The same content is at website http://cacreeks.com now.