Sanborn Fire Insurance Maps are a valuable resource for local history. The Sanborn Map Company was a publisher of detailed maps of U.S. cities and towns in the 19th and 20th centuries. The maps were originally created to allow fire insurance companies to assess their total liability in urbanized areas of the U.S. Since they contain detailed information about properties and individual buildings, Sanborn maps are invaluable for documenting the changes in the built environment of American cities over many decades.

ProQuest Digital Sanborn Maps (Cal Poly Login Required)

Cal Poly holds a subscription to digital access of California Sanborn Maps. The maps are in black and white. Access remotely with a Cal Poly account or on library computers/using campus wifi on your own laptop.

Sanborn Maps at the Library of Congress (free and public access, no login required)

The Library of Congress provides access to digitized Sanborn Maps in color. They are continuing to add more maps. To find SLO County maps, search for the town or search for "San Luis Obispo" to find all county maps.

1886 Sanborn Map of San Luis Obispo, Library of Congress Geography and Map Division

Interactive San Luis Obispo City Sanborn Mapping Projects:

From SLO City, the 1905 and 1950 Sanborn Maps side by side with a 2011 aerial

From Cuesta: San Luis Obispo Sanborn maps 1886 vs 1891

Maps of Private Land Grant Cases of California (circa 1840-1892) - hand-drawn property maps (disenos). Search "San Luis Obispo," includes many of the ranchos and the missions

Calisphere: Search across all California archives for maps by searching "city name" and "map"

1874 Map of San Luis Obispo County

Interactive map of the 1874 San Luis Obispo County Map: https://arcg.is/0GXrDf0, georeferenced from 1874 Map of the County of San Luis Obispo, California at UCLA's Special Collections

Rancho Boundaries of Central Coast and California

Interactive map outlining the boundaries of the ranchos of the Central Coast and California based on the Public Land Survey System.