Much of the State Route 140 alignment can be traced to the early years of Nevada's state highway system. A road roughly following about of the southern end of the current alignment was in place by 1919. However, instead of entering Oregon en route to Adel, the road veered westward through Washoe County towards Vya and Cedarville, California. By 1929, this alignment had been established as State Route 8A. The highway remained mostly unimproved for many years after designation by the state. The portion of highway from US 95 to Denio became a gravel road by 1940 and was not fully paved until 1953. The route was realigned near Denio Junction by 1949 (eliminating backtracking through Denio) and the portion between Denio and the California state line had been improved to a fully graveled road by 1952.