The Middle Fork of the Salmon River is a 104 mile stretch of river flowing through the heart of Idaho. It flows through the Frank Church River of No Return Wilderness; a part of the Salmon River Mountains. This is an incredibly isolated float that is far from civilization and can be exceptionally dangerous. That's why it's awesome.
This is a permitted float trip that requires about 6 days to complete. Permits are drawn as part of a lottery system (info here). Permits are limited to 7 launches per day, which keeps traffic on the river incredibly low. As a testament to how pristine this river is kept, all waste, including human and fire ashes, is required to be removed from the river sites (you have to take it with you).
This river is not for the faint of heart or the rafting newbie. It consists of over 300 rapids of class III-IV+. That means expert level for those not fluent in rapids classification. The elevation drop is over 3000 feet from start to finish. There are a number of fatalities every year on this river, and that includes people on guided outfitter trips. You have to be an expert on the sticks, and research and scouting on these rapids is a necessity (Forest service provides hazard updates and info here).
Within this whitewater rafting paradise is a fantastic wilderness fishery. Since 1973, the Middle Fork has been a catch and release, artificials only, single barbless hook regulated fishery. The Westslope Cutthroat population has flourished in these conditions. Coupled with a lack of pressure, this river becomes an incredible fishing opportunity. Primarily a dry fly fishery, the best fishing is outside of the lottery system's calendar in September. The already low traffic is reduced even further, and permits are available on a first come, first serve basis. Cutthroats are eager to feed as they fatten up for the impending winter. Water levels are much more favorable at this time of year as well. This is truly a once in a lifetime trip worthy of any angler's efforts.