the eastern edge of Yosemite and US 395 is designated as the Lee Vining Canyon Scenic Byway, a separate National Forest Scenic Byway. SR 120 is part of the California Freeway and Expressway System, and both the western portion and the eastern portion west of US 395 are part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. SR 120 is eligible to be included in the State Scenic Highway System, but it is not officially designated as a scenic highway by the California Department of Transportation. The Tioga Pass Road was designated as a California Historic Civil Engineering Landmark by the American Society of Civil Engineers in 2002. History During the Gold Rush, SR 120 was originally known as Big Oak Flat Road, after the village of Big Oak Flat through which it passes in the Sierra foothills. It was a pack trail from Stockton which became popular with prospectors about 1849. By 1874 it was a wagon road which extended to Yosemite Valley. In 1921, the California State Assembly authorized San Joaquin County to transfer the county road connecting Manteca with then-Route 5 (now I-5) at Mossdale to the state. It was numbered Route 66, as was a 1933 extension from Manteca east to Route 13 in Oakdale. Also in 1933, Route 40 was extended east from Mono Lake to Route 76 (US 6) at Benton. The route from Manteca to Benton was marked as Sign Route 120 in 1934, and was soon extended west to Mossdale, replacing what had been part of U.S. Route 99W. Priest grades West of Priest is a section of highway with over one hundred curves and hairpin turns, known as the "New Priest Grade." With a 4% grade, it opened in 1915 and was built by a group of local volunteers who desired an alternative to the very steep (17%) Old Priest Grade. Today, both grades are paved, but trailers and RVs are prohibited from Old Priest Grade. There is a 7,500-pound weight limit on the old grade. Major intersections See also References Map: "Stanislaus National Forest, California," U.S. Forest Service, 1979. External links A Brief History Of The Tioga Road Caltrans: Route 120 Road Conditions Tioga Road (Highway 120 through the Yosemite National Park) conditions California @ AARoads.com - State Route 120 California Highways: SR