One of San Francisco's most noteworthy works of architecture, the seven-story office block was designed by Willis Polk (1917) and named for Andrew Hallidie, inventor of the cable car. Because the facade is formed by a modular grid of glass panes hanging from a sturdy reinforced concrete frame, the building is considered the world's first glass-curtain-walled structure, a precursor of contemporary commercial architecture. In the local offices of the American Institute of Architects, a small gallery offers changing displays of architectural drawings and photographs. A post office and a clothing store occupy the ground floor.