MLA

Watkins, Carleton E., 1829-1916. Niantic Building, San Francisco. Watkins 1. [1880?]. https://collections.library.yale.edu/catalog/2056900.

APA, 6th edition

Watkins, Carleton E., 1829-1916. (["Watkins 1"])([1880?])[Niantic Building, San Francisco]. https://collections.library.yale.edu/catalog/2056900.