Madera County Road 600 is an approximately thirty-mile-long highway located in the Sierra Nevada Mountains. Road 600 begins at California State Route 49 near Ahwahnee and terminates to the south at Avenue 21. Road 600 historically was part of the Washburn Brothers Yosemite Stage Road to the Wawona Hotel and Yosemite Valley. Major waypoints along Road 600 include the ghost town of Grub Gulch and historic railroad terminus of Raymond.
https://www.gribblenation.org/2024/04/madera-county-road-600-and-post-1886.html?m=1
It seems this corridor was once under consideration as a 61-mile addition to the State Highway System between Madera and Mariposa Grove. According to the February 1925 California Highways & Public Works (Page 154 on the link below) the Legislature authorized a survey of the Yosemite Stage Road in 1921. The survey was completed in 1925 but was never acted upon:
https://archive.org/details/california192427highwacalirich/page/n163/mode/2up?view=theater&q=madera