MLA

Forsyth, James W. (James William), 1836-1906. Chicago, Ill.. Box 5, folder 86. 19th century. https://collections.library.yale.edu/catalog/2030409.

APA, 6th edition

Forsyth, James W. (James William), 1836-1906. (["Box 5, folder 86"])(19th century)[Chicago, Ill.]. https://collections.library.yale.edu/catalog/2030409.