Here are some links to sites related to Idaho’s Centennial Trail.

Idaho State Parks site, including Centennial Trail
Bureau of Land Management
Boise National Forest
Sawtooth National Forest
Payette National Forest
Salmon-Challis National Forest
Nez Perce National Forest
Bitterroot National Forest
Clearwater National Forest
Idaho Panhandle National Forests
Sawtooth National Recreation Area
Frank Church Wilderness information
Another Frank Church Wilderness site
Selway Bitterroot Wilderness information