Highway 139 has had many designations. In the 1870s, it was part of the failed Big Valley Toll Road. In 1929 it became the Lassen-Modoc Joint Highway 14. The mission was to build a 134-mile highway from Susanville to the Oregon border near Malin. Funding for the estimated $2.5 million project came from many sources. Where the road traversed through the Modoc National Forest it was that agency that was responsible for the cost of construction. They dubbed the route Forest Service Route No. 16, and dragged their feet with the project. In 1956 the route was finally completed and designated County Road A-1. In 1959, it officially became Highway 139.