State Highway 166 or SH 166 runs for 43.0 miles (69.2 km) from SH 118 near Nunn Hill in northern Jeff Davis County, Texas passing around a major portion of the Davis Mountains before ending at SH 17 about two miles south of Fort Davis. The highway is maintained by the Texas Department of Transportation (TxDOT).The scenic highway was originally a longer loop around the mountain range and was envisioned in 1927 as a "state park highway" until an actual state park could be established in the area.