The Trans-Sierra Highway was a potential highway project proposed to traverse the Sierra Nevada, connecting the Central Valley of California to regions eastward. The concept, which emerged in the 1920s, was ultimately never realized due to significant resistance from environmental conservationists and local communities.
The prospective highway was intended to join Mono and Madera counties. Environmentalists, however, expressed concern that the project would pose a serious threat to the area's natural wilderness. Particularly, the highway's proposed route was expected to intersect the headwaters of the San Joaquin River, causing potential harm to the surrounding ecosystem.[1]