The McKinley national memorial statue was modeled from this photograph The official post card for sale here.

Broadside advertising the sale of postcards showing reproduction of Frances Benjamin Johnston's 1901 photograph of "President McKinley delivering his last address, Buffalo, September 5, 1901."
Frances Benjamin Johnston Collection (Library of Congress).
Halftone copyright 1907 by Frances Benjamin Johnston; original photograph copyright 1901 by Frances Benjamin Johnston.