Railroad map of Michigan / prepared for the Commissioner of Railroads by O.W. Gray & Son.
MLA
Gray, O. W., and Son. Railroad Map of Michigan / Prepared for the Commissioner of Railroads by O.W. Gray & Son. O.W. Gray & Son, 1876. https://collections.library.yale.edu/catalog/15814485.
APA, 6th edition
Gray, O. W., & S. (1876). Railroad map of Michigan / prepared for the Commissioner of Railroads by O.W. Gray & Son. [Maps]. O.W. Gray & Son, https://collections.library.yale.edu/catalog/15814485.