A few words on Orange County rancho maps...

A friend recently asked me for a few cursory thoughts on local rancho maps. I thought I'd post part of my reply here, as it may be helpful to someone else someday.

The more artistic and fanciful Orange County rancho maps -- some of which were distributed as posters by title insurance companies -- are attractive and people love them. (The image below, also posted at https://www.flickr.com/photos/ocarchives/, is an example of one that's historically important more because it was created as a WPA project than because of its accuracy.) These are the rancho maps people see most often. They are good teaching tools and are generally relatively modern.

But these "pretty" maps usually aren't terribly helpful for determining exactly where the rancho lines were. For that, the best readily-available map is the fold-out one that came in the back of the early editions of the little "Old Spanish and Mexican Ranchos of Orange County" booklet by W. W. Robinson. Robinson was not only an excellent historian, but also happened to be the vice president of the Title Insurance & Trust Co., which published the booklet. (Shown at the top of this post. Also see https://www.flickr.com/photos/traderchris/2472347272/.)

Then there are the individual rancho maps filed with Los Angeles County (before O.C. separated from L.A.) which are sort of like tract maps on steroids. To a surveyor, these are the most accurate -- But how many of us can read surveyor-ese? And how many of their original reference points still stand? That said, they provide some interesting insights including landmarks that help define the rancho boundaries, including adobes, creeks, lakes, and the points where significant roads entered and left the rancho. They don't show as much detail in the center of the ranchos, as such detail doesn't help define the boundaries. Copies of these maps are available in the L.A. Maps series at the Orange County Archives.

Providing less survey data but much greater historical gee-whiz factor are the diseño maps, which were used by the Lands Commission to help identify lands claimed by the rancho owners. (See https://www.sos.ca.gov/archives/collections/disenos-collection/) Often of particular note on these maps are early place names and evokative illustrations of natural features.