MLA

Gray, O. W., and Son. Gray's Atlas, Nebraska. O.W. Gray & Son, 1873. https://collections.library.yale.edu/catalog/15814777.

APA, 6th edition

Gray, O. W., & S. (1873). Gray's atlas, Nebraska. [Maps]. O.W. Gray & Son, https://collections.library.yale.edu/catalog/15814777.