Cite

Philadelphia / [cartographic material] / O.W. Gray & Son.

MLA

Gray, O. W., and Son. Philadelphia / [Cartographic Material] / O.W. Gray & Son. O.W. Gray & Son, 0AD. https://collections.library.yale.edu/catalog/15811120.

APA, 6th edition

Gray, O. W., & S. (0 C.E.). Philadelphia / [cartographic material] / O.W. Gray & Son. [Maps]. O.W. Gray & Son, https://collections.library.yale.edu/catalog/15811120.