Theodore Roosevelt once declared himself to be "as strong as a bull moose." The appellation stuck and the moose became the popular symbol for the Progressive Party under Roosevelt. This cartoon depicting the mascots of the major parties appeared in Harper's Weekly, July 20, 1912, just before the "Bull Moose" convention opened in Chicago. The Latest Arrival at the Political Zoo Edward W. Kemble (1861-1933) Lithograph, 1912 Theodore Roosevelt Birthplace National Historic Site National Park Service, New York City