Cite

Thayer's map of the Black Hills and Big Horn Country.

MLA

Thayer, H. L. Thayer's Map of the Black Hills and Big Horn Country. H.L. Thayer, 1877. https://collections.library.yale.edu/catalog/15814718.

APA, 6th edition

Thayer, H. L. (1877). Thayer's map of the Black Hills and Big Horn Country. [Maps]. H.L. Thayer, https://collections.library.yale.edu/catalog/15814718.