MT 1 was first designated on October 9, 1922, near its present location. By 1924, its route had been designated as part of the National Parks Highway Auto Trail. This route followed the general path of MT 1, traveling from Opportunity through Anaconda and Philipsburg to Drummond. The overall length of the routing was approximately , and was generally an unimproved dirt road. By the next year, the National Parks Highway had been rerouted away from this route. The unsigned MT 1 had been rerouted, now with an overall length of approximately . Also by 1925, the portion of MT 1 traveling from its southern terminus to Anaconda had been paved. Also, the section of the highway near the town of Brown traveling to Stone had been graded, while the rest of the route remained unimproved dirt. By at least 1927, MT 1 had been rerouted, with an overall length of approximately , and the portion of the highway traveling from Stone to its northern terminus had been graded. At least two years later, the entire length of the route had been graded. In 1934, the portion of MT 1 that traveled from modern-day milepost 24.190 to the Deer Lodge-Granite County border was reconstructed along its current route.