MLA

G. W., et al. Colton's Map of the County of Westchester / Drawn, Engraved and Published by G.W. & C.B. Colton & Co. G.W. & C.B. Colton & Co., 1877. https://collections.library.yale.edu/catalog/15762488.

APA, 6th edition

G. W., Colton, C. B., & C. (1877). Colton's map of the county of Westchester / drawn, engraved and published by G.W. & C.B. Colton & Co. [Maps]. G.W. & C.B. Colton & Co., https://collections.library.yale.edu/catalog/15762488.