Tallest Building in North America: Willis Tower, Chicago

The Willis Tower (formerly Sears Tower) in Chicago, Illinois, stands as the tallest building in North America at 1,451 feet (442.1 meters) to architectural top (1,729 ft / 527 m to tip including antennas).

Key Facts

• Floors: 108
• Completed: 1974 (as Sears Tower)
• Architect: Bruce Graham / Fazlur Rahman Khan (Skidmore, Owings & Merrill)
• Structural system: Bundled tube — 9 steel tubes of varying heights, revolutionary for supertall efficiency
• Renamed: 2009 (Willis Group lease)
• Observation deck: Skydeck (103rd floor, 1,353 ft) — 1.7M visitors/year

North American Supertall Context (2024)

Critical distinction: One World Trade Center is taller by architectural height (spire counts). Willis Tower is taller by roof height (1,451 ft vs. 1,368 ft) and occupied floor height. CTBUH (Council on Tall Buildings) recognizes One WTC as tallest in Americas by architectural height; Willis leads by roof/occupied height.

Why It Matters

Willis Tower's bundled tube system (Khan's innovation) made supertalls economically viable—less steel per square foot than Empire State Building. It held world's tallest title for 24 years (1974–1998). It remains an engineering icon and Chicago's vertical identity.