Re: Yellowstone or Wind River
Well both Yellowstone and the Wind River offer what it seems you are looking for. The Wind River area also offers the opportunity to catch some great Golden Trout in many of the little lakes through out that Mt Range.
If you wish to fish the Yellowstone back country you need to get in touch with the Park before you come. Find out the regulations and what areas are open. There are specific back country sites that you will have to camp in. These are not camp grounds. They are individual sites spread out over the back country. Some are first come first serve others must be reserved in advance. August is a good time as some back country areas are closed until that time due to bear activity.
One trip you might want to inquire about would be the Upper Yellowstone. Take a shuttle boat across the lake and then hike in from there up the South East Arm. Many lakes and small creeks and very remote stretches of the Yellowstone headwaters.
But I recommend you get in touch with the Park prior to coming out. They can help you plan a great back country hiking fishing trip.