seri Willis Tower Som Chicago USA ArchEyes skyscraper Sears
The Willis Tower | © Seri

Completed in 1974 by Skidmore, Owings & Merrill (SOM), the Willis Tower, formerly known as the Sears Tower, stands as a spectacular achievement in modern engineering and design. Rising above the Chicago skyline, this iconic edifice symbolizes American architectural innovation, testifying to SOM’s unwavering commitment to progressive construction methodologies and pioneering design principles.

The inception of the Willis Tower traces back to the late 1960s when Sears, Roebuck and Company, then the world’s largest retailer, required a new headquarters. The challenge lay in creating a structure that could comfortably house its burgeoning workforce. Responding to this daunting task, SOM crafted a design that was not only revolutionary but also impeccably suited to the company’s needs. This marked the genesis of the iconic Willis Tower, a remarkable blend of architectural innovation and practical functionality.

Willis Tower Technical Information

  • Architects1-7: SOM
  • Principle: Bruce Graham
  • Location: Chicago, Illinois, United States
  • Topics: Skyscrapers
  • Cost: $175.000.000 USD
  • Height: 527,3m
  • Project Year: 1970-1974
  • Photographs: Various Sources, refer to the individual photo captions

Architecture is the design of space that contains, cuddles, exalts, or stimulates the persons in that space.

– Bruce Graham8, a partner at SOM

Willis Tower Photographs

Willis Tower Som Chicago USA ArchEyes skyscraper Sears sebastian arroyo
© Sebastian Arroyo
Willis Tower Som Chicago USA ArchEyes skyscraper Sears gautam krishnan
© Gautam Krishnan
Willis Tower Som Chicago USA ArchEyes skyscraper Sears pedro lastra
© Pedro Lastra
Willis Tower Som Chicago USA ArchEyes skyscraper Sears cody engel
© Cody Engel
Willis Tower Som Chicago USA ArchEyes skyscraper Sears billy freeman
© Billy Freeman
Willis Tower Som Chicago USA ArchEyes skyscraper Sears noel forte
© Noel Forte
tim trad Willis Tower Som Chicago USA ArchEyes skyscraper Sears
© Tim Trad
triyansh gill Willis Tower Som Chicago USA ArchEyes skyscraper Sears
© Triyansh Gill


Groundbreaking Design and Construction

The chief architectural engineer for the project, Fazlur Rahman Khan, devised a novel “bundled tube” structural system for the tower. This system was not only incredibly efficient—allowing for less steel to be used compared to other building methods—but it also gave the tower its distinct, stacked appearance. The Willis Tower was composed of nine square tubes, bundled together to form a unified structure. At the base, all nine tubes reached up to the 50th floor, while fewer tubes continued to rise with increasing height, resulting in the building’s distinctive tiered silhouette.

At the time of its completion in 1973, the Willis Tower was the tallest building in the world, standing at an impressive 1,450 feet (443.2 meters) and offering 108 stories of usable office space. Notably, it was the first building to surpass the height of New York City’s North Tower of the World Trade Center. The Willis Tower would retain the title of the world’s tallest building for 25 years until it was eventually surpassed by the Petronas Towers in Kuala Lumpur, Malaysia, in 1998.

A Cultural Landmark and Sustainable Icon

The Willis Tower is not merely an office building; it has always served as an integral part of Chicago’s cultural and social fabric. The tower’s Skydeck, located on the 103rd floor, provides unparalleled views of Chicago and, on a clear day, allows visitors to see as far as four neighboring states. In 2009, the Skydeck underwent a significant transformation with the addition of The Ledge, four glass balconies extending four feet beyond the building’s facade, offering brave visitors a vertigo-inducing view of the city below.

A significant part of the Willis Tower’s design was the incorporation of environmental sustainability. The building was awarded the Energy Star label in 1999, and in 1984 it was recognized as an official city landmark. Over the years, several energy-saving renovations have been carried out, including the installation of a green roof and upgrades to the building’s heating and cooling systems.

Despite its age, the Willis Tower remains a potent symbol of Chicago’s architectural heritage and a significant testament to the innovative design and engineering capabilities of SOM. Its monumental scale, innovative design, and the engineering prowess it embodies continue to captivate architects, engineers, and the general public.

Legacy and Influence on Skyscraper Design

In 2015, the Willis Tower underwent a significant renovation as part of a larger revitalization project for the building. The $500 million renovations aimed to bring new retail spaces, dining options, and entertainment venues to the lower levels of the tower. Also, the upgrades included improvements to the tower’s energy efficiency, ensuring that the Willis Tower continues to be an example of sustainable architectural practices.

The legacy of the Willis Tower is not merely in its grandeur and the pioneering techniques employed in its construction. It’s a legacy that has fundamentally shaped the discourse around skyscraper design. It challenged the conventions of tower design,

introducing a structural system that revolutionized the way high-rise buildings are conceived. The “bundled tube” concept has since influenced the design of other skyscrapers worldwide and continues to be studied and admired by aspiring architects and engineers.

Economic, Cultural, and Educational Impact

One cannot ignore the economic and social impact the Willis Tower has had on the city of Chicago. As the home to hundreds of businesses and organizations, it has become a vital hub of commercial activity. It has attracted businesses from around the world, contributing to the city’s status as an international center for commerce. The tower has also created a vibrant community within its walls, with numerous facilities, amenities, and services designed to support the diverse needs of its occupants.

In addition to its functional role, the Willis Tower has also become a beloved part of Chicago’s cultural identity. The annual SkyRise Chicago event, where participants climb the tower’s 2,109 stairs, has become a cherished tradition. The tower has also featured prominently in popular culture, appearing in numerous films, television shows, and other media.

Furthermore, the Willis Tower’s Skydeck has transformed the tower into a popular tourist destination. The Ledge, with its thrilling views of the city below, attracts millions of visitors each year. These visitors not only contribute to the local economy but also carry with them the story of the Willis Tower, spreading its fame across the globe.

The Willis Tower also holds educational significance. It serves as a real-world example of the concepts taught in architecture and engineering courses. Its design and construction have been studied in countless classrooms, inspiring students to push the boundaries of what’s possible.

Willis Tower Plans

Willis Tower Som Chicago USA ArchEyes skyscraper Sears diagram
Elevation and Section | © SOM
Willis Tower Som Chicago USA ArchEyes skyscraper Sears floor plan
Floor Plan | © SOM
Willis Tower Som Chicago USA ArchEyes skyscraper Sears plan
Floor Plan | © SOM
Willis Tower Som Chicago USA ArchEyes skyscraper Sears plans
Floor Plans | © SOM
Willis Tower Som Chicago USA ArchEyes skyscraper Sears diagram
Structural Diagram | © SOM

About SOM

Skidmore, Owings & Merrill (SOM) is a prestigious global architectural, urban planning, and engineering firm. Founded in 1936, the firm is known for its innovative approach, technical excellence, and design of high-performance, sustainable buildings and cities. SOM’s renowned projects include the Willis Tower (formerly known as the Sears Tower) and the Burj Khalifa, currently the tallest building in the world. Their work consistently pushes the boundaries of design and construction, resulting in some of the most iconic structures worldwide that exemplify modernist architectural style, structural innovation, and thoughtful integration with their urban environments.
Works from SOM 

  1. Engineer: Myron Goldsmith
  2. Structural Engineer: Fazlur R. Khan
  3. Developer: Sears, Roebuck & Company
  4. Weight: +225.000tn
  5. Roof Height: 442.14 m
  6. Top Floor Height: 412.69m
  7. Elevators: 104
  8. Bruce Graham, Som by Stanley Tigerman