MLA

Lloyd, H. H., and Co. Lloyd's Military Maps : Showing the Principal Places of Interest / Compiled from Official Data by Egbert L. Viele and Charles Haskins. H.H. Lloyd :, Published under the auspices of the American Geographical and Statistical Society, 1861. https://collections.library.yale.edu/catalog/15811189.

APA, 6th edition

Lloyd, H. H., & C. (1861). Lloyd's military maps : showing the principal places of interest / compiled from official data by Egbert L. Viele and Charles Haskins. [Maps]. H.H. Lloyd :, Published under the auspices of the American Geographical and Statistical Society, https://collections.library.yale.edu/catalog/15811189.