There are many great rides in the Williams Summit area. Ranging from easy out and back two track forays to great single track to epic exploration to super sweet downhills
From Salmon, drive south on US93 about 6 miles. Turn right at Shoup Bridge, cross the Salmon River and stay on the paved road until it turns to gravel. From the end of the pavement, the first Trailhead is about 6 miles, Williams Summit is about 10 miles. There are a few trailheads in between.
http://www.singletracks.com/item.php?c=1&i=3736