MLA

Sanborn Map Company, cartographer. Insurance Maps of San Francisco, California. Sanborn Map and Pub. Co., 1881. https://collections.library.yale.edu/catalog/33192586.

APA, 6th edition

Sanborn Map Company, cartographer. (1881). Insurance maps of San Francisco, California [Maps, Atlases, Fire insurance maps]. Sanborn Map and Pub. Co. https://collections.library.yale.edu/catalog/33192586.