 The highway was first designated in 1945 and over the years was gradually extended outward from Presidio.Eastern portions of the road in Brewster County, however, had several previous highway designations going back to 1939.In addition to SH 118 in Study Butte, FM 170 has highway intersections in Presidio with U.S. Route 67 and its auxiliary route Business U.S. Route 67-A along with State Highway Spur 203.