The Appalachian Trail is the grandaddy of American long distance walking trails, it is relatively old and was specifically designed to get people in to the wood

The Appalachian Trail is the grandaddy of American long distance walking trails, it is relatively old and was specifically designed to get people in to the woods - even it has bits of road shoulder. While there may be examples of long "trails" in the US that are entirely exclusive of "road", they're certainly not common.