The Forest Service lists it as 101 miles. Some people consider the “corridor” the dirt and gravel section, and others consider it the whole route between Elk City and Darby, which includes some stretches of pavement and is longer than 101 miles.
The Forest Service says, “Travel time varies, but it takes eight to 10 hours to travel from Red River to Darby without rest stops. The average speed will be 12-15 miles per hour. A two-day trip is ideal with an overnight stay at one of the dispersed or primitive campsite locations.”
Time also depends on how recently it’s been graded and what kind of vehicle you’re driving. For example, Zimowsky took his four-wheel-drive van and spent several days and camped. I took my motorcycle and crossed it in a less than a day, which included a few stops and side trips.
You access it from the west to east by driving north on U.S. 95 to Grangeville and then cutting across to Red River, or from the other direction by heading to Stanley and then taking U.S. 93 north to Salmon and Darby.