Below, 1915 map for new auto travelers, provided by Hamburger Auto Supply in Los Angeles...they sold goggles.
Notice the "30% Grade" and the "Pass Through Snowshed" notes...refering to the photos on the 1800s Photos page.
Below, the first California state survey of this road was made in 1915, 6 years after the state acquired it. Was the basis for the AAA map and any other travelers map.
Above and below, 1916.
Everything was taking off in 1915-16 due to the car.
Below, letters related to the access to the old state road.