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Description

An Important Early Cadastral Map of San Mateo County

Rare early copy of perhaps the earliest map of San Mateo County, originally published by Britton & Rey in San Francisco.  

Oriented with east at the top and extending to cover all of San Franciso at the left, the map illustrates a number of Ranchos, early towns, roads, rivers, some topography and the progress of the early township surveys in San Mateo County.  The map includes teh names of dozens of early land owners and the details of a number of San Mateo County's earliest towns, including Menlo Park Villa Association, San Mateo, Redwood City,  Belmont, Spanishtown (Half Moon Bay), Ravenswood (East Palo Alto), 

The property of AJ Easton includes an early race course and the line of the San Francisco & San Jose Rail Road.

The original map, printed on 6 sheets sheets, was created following a  resolutioon of the County of San Mateo Board of Supervisors on October 4, 1864.

Rarity

Both the original 6 sheet map and this smaller example are extremely rare. 

Blueprint & Blue Line maps (Cyanotype Printing)

Blueprint and blue line maps were among the most popular means for the swift printing of maps for which there would be a limited demand. A blueprint or blue line map could be made and/or revised much more quickly than a lithograph, cerograph, or other printing method, and at a much lower cost.

This method of printing was invented in 1842 by John Herschel, a chemist, astronomer, and photographer. A cyanotype process, one starts by drawing on semi-transparent paper, weighted down by a top sheet of paper. The paper would be coated with a photosensitive chemical mixture of potassium ferricyanogen and ferric ammonium citrate. The paper would then be exposed to light, wherein the exposed portions turned blue and the drawn lines, protected from exposure, would remain white.

The cyanotype printing process was an improvement on the expensive and time-consuming method of hand-tracing original documents. The technique was particularly popular with architects; by the 1890s, a blueprint was one-tenth the cost of a hand-traced reproduction. It could also be copied more quickly.   

Blueprint and blue line maps began to appear as early as the 1850s and 1860s, but they really began to become the standard for mining and similar limited-purpose maps by the 1880s. The ability to create these maps quickly and at a low cost made them the standard for short-run prints, ideal for mapping mining regions in the West and for similar purposes.

The method still exists today, but in a very limited fashion. In the 1940s, diazo prints (whiteprints or bluelines) became more popular, as they were easier to read and faster to make. The blue lines on a white background of these prints are now what most people call blueprints.

Condition Description
Minor foxing.