There are a number of sites scattered around Los Altos Hills which are marked (for example) as "Historical Site Number 1".
Two examples of such markers are shown here:
Located at the intersection of O'keefe Lane with Normandy Lane - under a Pepper tree on the South side of O'Keefe
Located at St. Luke's Chapel in the Hills, on Duval Way
The details of how these markers came about, or exactly what weight or meaning should be attributed to these sites was unclear.
Moreover, only a few such markers were found, gaps in the numbering seemed to indicate that some (most) were unknown and/or missing,
Eventualy a Xeroxed copy of (what appears to be) a draft of a booklet describing these sites was located, the Author is thought to be Florence Fava. It appears to be a typewritten draft
but has no title page or indication of who authored it and when.