In southwest Wyoming at the Green River, south of the mouth of the Big Sandy River, a branch of the Oregon Trail splits away from the route to Fort Bridger. The branch follows up the east bank of the Green River to a point just south of the present Fontenelle Dam, crosses the Green and heads west up Slate Creek. Eventually this ''Slate Creek Cutoff'' joins another branch of the Oregon Trail, called the Sublette or Greenwood Cutoff, at a point on Oyster Ridge about twenty miles west of the Green River. A few miles southeast of that junction is Emigrant Springs, a popular campground on the Slate Creek Trail, and a mile south of Emigrant Springs are the Johnston Scout Rocks. It may be that those who broke their journey to rest at Emigrant Springs had to travel some distance down Emigrant Creek before finding a suitable campsite. Hence, Johnston Scout Rocks served as a register for some of those early travelers. Although inscriptions span the years 1850 to 1888, the names of the rock derives from the inscription, ''T.C. Johnston'' and ''1860 Scouts''.