According the mapping program we use for caching, this cache is placed at the north end of Cacheville Road, in the town of Yolo, in Yolo County. If you proceed north on Cacheville Road from this cache and cross the intersection with County Road 17 you are then driving on County Road 99W.
County Road 99W was, back in the day, the western branch of U.S._Route_99 coming from the US/Mexico border and continuing north to the border with Canada. The split between US 99W and US 99E occurred north of Sacramento and ended when they rejoined in Red Bluff. A similar split occurred in the Willamette Valley of Oregon.
In the 1850s, this community was known as Cacheville. The name was changed to Yolo when Yolo City was renamed as Woodland when Woodland became the county seat of Yolo County.