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Scarce City and County map of San Francisco, from an early Thomas Brothers Western States Atlas.

Thomas Bros. Maps was founded in 1915 in Oakland, California, by cartographer George Coupland Thomas and his two brothers, who developed a distinctive page-by-page grid system of mapping cities that eliminated the need for clumsy folding maps. The maps were bound in a convenient book format that became known as the "Thomas Guide." Since then, Thomas Guides have become the standard street reference for drivers in many West Coast communities as well as for police and fire departments, utilities, realtors, and local governments.