The large area outlined above, from the water tower on the far west, to the cemetery on the east side of Highway 92, was once the "San Mateo County Poor Farm and Hospital" .
As it says at the link above, "In the mid-1870's, the San Mateo County Board of Supervisors acknowledged the need to house the county's ill and indigent citizens. The County acquired this 140 acre parcel of ranch property in the hills west of San Mateo/Belmont. The San Mateo County Poor Farm & Hospital opened at this location in July of 1876."
Polhemus Road, which turns into Ralston Road when it crosses HWY 92, was called "Poor House Road" in old maps. There are old fruit trees, odd staircases with railings, and rock walls designating building foundations all over this hillside.
The Cemetery was in the east-most corner of the property, on the other side of Highway 92. The linked page above includes another link tab that will take you to a burial list of the over-500 people that were buried there from 1885 thru 1839. The graves are still there, but there is no access to the area. The Belmont Historical Society has one of the Cemetery's old wooden grave markers on exhibit in its "History Room". The graves were mapped by cadaver dogs in the 1990's.