Designed for the publisher of the Baltimore Sun, the nine-story Sun Building is one of the nation's oldest surviving skyscrapers, defined by its curtain walls, its internal metal structural frame, and the interior elevator. The soaring, three-bay exterior is divided into three major sections: a two-story triple-arch base, a five-story shaft of two tiers of projecting bay windows, and a crowning section marked by paired windows. The Sun Building also is of historic interest for its association with Alfred B. Mullett's postgovernment career, during which he contributed substantially to the early development of metal frame construction.