Thomas M. Callahan, one of the founders of the Golden Rule Stores, which evolved into the J. C. Penney Company, built one of Longmont's finest mansions. This two-and-one-half-story Queen Anne Style house is frame faced with red brick on a foundation of Lyons sandstone. Although the carriage house is original, the main dwelling's two-story rear addition, second-story balconies, wrap-around porch, and porte-cochère were turn-of-the-century additions. In 1908, the Callahans had a Chicago landscape firm plant the formal Italian garden. Mitchell and Halback, also of Chicago, redecorated the interior. They Neoclassicized the house, using a different exotic hardwood in each downstairs room and leaded glass windows. When Callahan retired to California in 1938, he donated the house to Longmont, which has used it ever since as a community center.