Cite

Map of the cities of Pittsburgh, Allegheny and environs.

MLA

Polk, R. L., and Co. Map of the Cities of Pittsburgh, Allegheny and Environs. R. L. Polk and Co., 0AD. https://collections.library.yale.edu/catalog/15811125.

APA, 6th edition

Polk, R. L., & C. (0 C.E.). Map of the cities of Pittsburgh, Allegheny and environs. [Maps]. R. L. Polk and Co., https://collections.library.yale.edu/catalog/15811125.