Tallest Building in Chicago: Willis Tower at 442m

The tallest building in Chicago is the Willis Tower, which rises 442 meters (1,451 feet) above the city across 110 floors. Completed in 1973 as the Sears Tower and renamed in 2009, it reigned as the world's tallest building for 25 years and remains the third-tallest building in the Western Hemisphere today.

The Willis Tower at a Glance

Standing on the western edge of Chicago's Loop, the Willis Tower dominates the skyline of one of America's great architectural cities. Its 442-meter roof height is matched by twin antennas that push the structure's total tip height to 527 meters (1,729 feet). For an entire generation, this dark, stepped monolith was simply the tallest building on Earth, and even now it is surpassed in the Western Hemisphere only by One World Trade Center and Central Park Tower in New York.

The tower was conceived for the retail giant Sears, Roebuck and Company, which needed to consolidate thousands of employees into a single headquarters. The result was not just an office block but a statement of American corporate ambition during the early 1970s, a building that redefined what a skyscraper could be and how tall it could practically reach.

The Bundled Tube: Engineering Genius

The Willis Tower was designed by architect Bruce Graham and structural engineer Fazlur Rahman Khan of Skidmore, Owings & Merrill (SOM). Their defining contribution was the "bundled tube" structural system, an idea that changed skyscraper design forever. Instead of relying on a single rigid frame, the building is composed of nine square tubes, each 75 feet (about 23 meters) wide, bundled together into one massive base measuring 225 feet on each side.

The brilliance of the design lies in how those tubes behave. As the tower climbs, individual tubes terminate at staggered heights: two end at the 50th floor, two more at the 66th, and three at the 90th, leaving just two tubes to carry on to the full 110 stories. This produces the building's instantly recognizable stepped silhouette while drastically reducing the steel needed and resisting the powerful winds that sweep across Lake Michigan. The approach was so efficient that it used less structural steel per square foot than the much shorter Empire State Building, and it became a blueprint copied by tall buildings around the world.

Building Specifications

• Height: 442 m (1,451 ft) to roof; 527 m (1,729 ft) to antenna
• Floors: 110
• Architect: Bruce Graham / Fazlur Khan (SOM)
• Completed: 1973
• Cost: $175 million (1973 dollars)
• Use: Offices, observation (Skydeck Chicago)

Beyond the headline numbers, the tower contains roughly 4.5 million square feet of floor space, served by more than 100 elevators and over 16,000 windows that require regular automated washing. At its peak it housed about 12,000 Sears employees, and today it remains one of the busiest commercial addresses in the United States.

Skydeck Chicago and The Ledge

For most visitors, the heart of the experience is Skydeck Chicago, the observation deck on the 103rd floor at a height of 412 meters. It draws more than 1.7 million visitors each year, making it one of the most popular attractions in the Midwest. The fastest elevators whisk guests to the top in about a minute.

The Skydeck's signature feature is The Ledge, a set of fully glass boxes that cantilever 4.3 feet (1.3 meters) out from the building's western face. Standing inside one, visitors hang over the streets of Chicago with nothing but a transparent floor beneath their feet, a thrilling and slightly terrifying perspective. On a clear day, the view stretches across four U.S. states: Illinois, Indiana, Wisconsin, and Michigan.

From Sears Tower to Willis Tower

The building opened in 1973 as the Sears Tower, a name it carried for 36 years. By the late 1980s, however, Sears had begun moving operations out of the building, and in 2009 the London-based insurance brokerage Willis Group Holdings leased a large portion of the space. As part of that deal, the company acquired the naming rights and the tower was officially rechristened the Willis Tower. The change was unpopular with locals: to this day, many Chicagoans stubbornly continue to call it the Sears Tower, treating the original name as part of the city's identity.

How It Compares

When it was completed, the Willis Tower seized the title of world's tallest building from New York's World Trade Center, and it held that crown until 1998, when the Petronas Towers in Kuala Lumpur edged it out on a technicality involving their spires. Today it ranks well outside the global top ten, dwarfed by megatall structures such as the Burj Khalifa in Dubai. Yet in the Western Hemisphere it still holds third place, and within Chicago it stands comfortably above its nearest local rivals, the Trump International Hotel and Tower and the Aon Center. For more on the world's record-holders, see our guide to the tallest building in the world and our look at the tallest mountain in the world.

Key Facts

• Location: 233 South Wacker Drive, Chicago, Illinois, USA
• Height: 442 m (1,451 ft) to roof, 527 m (1,729 ft) to antenna tip
• Floors: 110
• Completed: 1973 (as the Sears Tower)
• Structural system: Bundled tube, nine interconnected tubes
• World's tallest building: 1973 to 1998 (25 years)
• Observation deck: Skydeck Chicago, 103rd floor (412 m)

Fun Facts

• Many Chicagoans still refuse to call it Willis Tower, preferring the original Sears Tower name.
• The building's antennas were originally white but later painted dark to reduce their visual impact.
• Fazlur Khan's structural innovations earned him the nickname the "Einstein of structural engineering."
• The tower's upper floors can sway several feet in high winds, a deliberate feature that lets the structure flex rather than break.

Frequently Asked Questions

Why was the Sears Tower renamed the Willis Tower?

In 2009, the insurance brokerage Willis Group Holdings leased a significant portion of the building and negotiated the naming rights as part of the agreement. Sears had largely vacated the tower years earlier, so the name no longer reflected its main occupant.

Is the Willis Tower still the tallest building in the United States?

No. It was the tallest in the U.S. and the world for decades, but One World Trade Center and Central Park Tower in New York are now taller. The Willis Tower remains the tallest building in Chicago and the third-tallest in the Western Hemisphere.

How many states can you see from the Skydeck?

On a clear day, visitors on the 103rd-floor Skydeck can see four states: Illinois, Indiana, Wisconsin, and Michigan, along with the vast expanse of Lake Michigan.

What makes the bundled tube design special?

The bundled tube uses nine connected structural tubes that end at different heights, creating the tower's stepped shape. It allowed the building to reach record heights using less steel and to resist strong winds, and it influenced skyscraper engineering worldwide.