The Shoshone Indians used this trail system to cross the mountains between Cache Valley and Bear Lake Valley, and on into Wyoming. When Mormon settlers came, they used the trail to take mail between the valleys. A marker commemorating the pioneer mail route is located up Cub River Road (County Road 406 which turns off US Hwy 91 about four miles south of Preston, Idaho). The markers are about 12 miles up Cub River Road. When you get to the fork in the road, take the Willow Flat, Franklin Basin turn. There are two markers; one at Thomas Spring and one a little further on.