The Big Store seen from Lake Michigan (© Randall Krause)

Sears Tower stands tall, over 1,700 feet aloft, overlooking the west side of Chicago's downtown Loop. Clad in bronze-tinted glass and stainless aluminum, rising with determination yet elegance from the depths of its grand foundations to the tips of its massive spires, luring tourists in daze, housing a workforce of thousands, the Big Store represents an era in Chicago of optimism and opportunity that will not be forgotten.

Sears Tower is currently the tallest steel-framed skyscraper in the world. With a rooftop height of 1,450 feet, it also retains the longstanding title of highest rooftop of any office building in the western hemisphere, even eclipsing One World Trade Center in New York City.

Did You Know? officially launched in July of 1998, marking the 25th anniversary of the landmark tower, making it the longest running enthusiast site for any skyscraper worldwide.


Early Years

Modern versus classic in Chicago's Loop (© Randall Krause)

Originally designed in the late 60's by Bruce Graham of Skidmore, Owings, and Merrill for Chicago-based Sears, Roebuck and Co, Sears Tower was officially topped out on May 3, 1973.

During the skyscraper's initial construction, which began in August of 1970, two other prominent office tower projects vied for the "world's tallest" title: the Standard Oil of Indiana Building (now the Aon Center) located in downtown Chicago and the World Trade Center high-rise complex formerly located in Manhattan. Both were surpassed within their first year of completion by Sears Tower, which opened its doors on September 10, 1973.

In 1984, SOM was commissioned to overhaul many of the tower's lower-levels, including the addition of a vaulted atrium alongside Wacker Drive. Following Sears' departure, the building underwent a comprehensive renovation by DeStefano + Assoc of all public and Skydeck lobbies and elevators. This also included the construction of two glass-and-steel canopies over the Franklin Street and Jackson Street entrances. By the fall of 1995, a seasonal rooftop illumination program was also initiated. Much like the Empire State Building, the colors typically coincide with national events and holidays.

Sears Tower was the last supertall building constructed during the International architecture period, and SOM's interpretation of the style is remarkably bold and awe-inspiring.

The superstructure consists of nine interlocking tubes that terminate at different heights, creating the iconic stepped-back appearance of the tower. Each tube is a rigid steel frame that performs in tandem with its neighbor to efficiently counteract all lateral and gravity loads. This is in contrast to the popular tube-in-tube system, in which a rigid network of floor diaphrams and closely-spaced exterior columns work in unison to resist lateral loads whereas a centralized core functions to carry vertical loads exclusively (e.g. as implemented in the World Trade Center towers.)

This "bundled-tube" configuration was a revolutionary engineering concept at the time, pioneered by SOM's very own Fazlur R. Khan. It allowed for large open office spaces on the lower levels, where Sears, Roebuck and Company would reside, and smaller floor plates on the upper levels with unobstructed views of the cityscape. To aid in occupant comfort, belt trusses were rigged on the upper mechanical floors thereby further reducing shear forces (i.e. wind-induced sway).

Building automation was a primary design consideration as well. For fire, security, and HVAC monitoring and control, engineers opted for a Honeywell computer system, one of the largest such networks ever installed at the time. Another technological innovation was the robotic window washers that could be programmed to descend along tracks built into the curtain wall. Currently, they operate eight times per year.

Sears Tower also provides facilities for broadcasting to the Chicago metropolitan area. Twin 67-foot cylindrical supports, both 12-feet in diameter, project from inside the roof to provide a rigid steel base for 159-foot communication towers, which are comprised of triangular supports and antenna pylons, all of which is encased in white fiberglass radome to prevent large diameter ice formation, extending the full building height. The 101st floor is leased to broadcasters for housing of transmitter equipment.

Vertical transporation was also crucial. Designers had to ensure efficient flow of pedestrian traffic throughout the building — which, on any given day, could number in the tens of thousands. Westinghouse Electric Corp. employed "skylobbies" for this purpose, a system which Otis Elevator Co. had originally implemented in Chicago's own John Hancock Center. Designated transfer-floors would be served by banks of double-deck express elevators. Separate banks of local-service elevators would carry passengers to their final destination.

Did You Know?
Due to its excessive height, Sears Tower was designed to lean approximately six inches from normal to counteract for the rotation of the Earth -- a fact that engineers later discovered was unnecessary. Other resources erroneously claim that this lean is the result of unequal loads bearing on its foundations.


Modern Day

Looking skywards on South Wacker Drive (© Randall Krause)

Sears eventually chose to move its headquarters to a more human-scale suburban setting in Hoffman Estates leaving the tower nearly half vacant. Management and leasing of the property was initially given to Chicago developer John Buck Co. — who established the iconic building as a destination for many new tenants over the course of almost five years.

The building was first acquired in 1989 by Boston's AEW Capital Management for the sum of $800 million. However, despite successfully bringing occupancy up by 40 percent during its term of ownership, AEW could not profit leasing space to its roster of tenants due to a continued downtown real estate depression and lower than average rental rates within the Tower.

In late 1997, the landmark tower was sold for $804 million to Toronto-based TrizecHahn, a REIT (real estate investment trust) firm. Downtown property markets subsequently began to show signs of recovery, and Sears Tower was again becoming one of Chicago's most prestigious high-rise properties. In fact, to honor Sears Tower's principal structural engineer, an adjacent street was, following a ceremony in the building, dedicated "Fazlur R. Khan Way" on July 7, 1998 by the City of Chicago.

Sears Tower, alongside John Hancock Center and Amoco Building, was the epitome of the Chicago skyscraper craze during the latter half of the 20th century — a time when the American economy was booming and tall buildings were a sign of commercial strength and success.

To meet the growing demands of the digital age, Sears Tower was upgraded March 8 of 2000 with four combination antennas, each 29.4-feet, 2890-lbs mounted on 80-foot towers at the four corners of the roof. An Erickson S-64F Aircrane was used to lift the load from the top of the parking garage skyward about one quarter mile. Four city blocks were closed off during the massive operation. However, the addition would ensure that the Chicago area was capable of receiving HDTV.

On June 4, 2000, the 220-foot western communications tower had to undergo modifications to increase the signal quality of Chicago's local NBC television station. This necessitated disassembling the existing framework via hellicopter and installing a new 75-foot, 19250-lb stack of self-supporting antenna pylons for WMAQ-29, WLS-52, and WPWR-52/22 on top of the existing support tower, thus raising the height of the building to 1729 feet.

Following the attacks of September 11, 2001, however, the status of Sears Tower as a viable investment opportunity proved questionable. Trizec Properties Inc. finally transfered ownership to its lender, MetLife Inc., in August of 2003 after facing the growing possibility of defaulting on its mortgage. Less than one year later, however, MetLife sold its stake in the building outright to a group of three investors (including two of Larry Silverstein's group), thereby forming 233 South Wacker LLC.

The building was leased and managed by real estate firm CB Richard Ellis Inc. until 2007 when responsibilities were assigned to Chicago-based U.S. Equities Realty LLC. Seeking to revitalize and redevelop Sears Tower, owners have announced numerous "green initiatives", including possible LEED certification, aimed at reducing energy costs and positioning the Tower as a more attractive and eco-friendly destination for new tenants. Visionary plans to "paint" the building silver were also briefly considered, but never left the drawing room table.

Engineers sought different ways of emphasizing the city of ‘broad shoulders’, and the desire for Chicagoans (including their businesses) to always be bigger, bolder, and better. Sears Tower is perfectly reminiscient of a thriving, innovative period in Chicago architectural history.

The entire building has also undergone significant security improvements since 2001. Johnson Controls' Hillside office was awarded the contract to install various barricades along all street-level entrances, X-ray metal detectors in the main concourse, and electronic turnstile portals around the elevator lobby. Additionally, visitors now wishing to do business in the tower must sign-in at a security checkpoint. Any unidentified person will be immediately escorted out of the building by armed security officers.

In 2015, private equity giant Blackstone Inc. purchased the Willis (née Sears) Tower and began a half-billion-dollar renovation that would radically change the role the former tallest building in the world would play in downtown Chicago.

Today, anyone — not just workers in the 108-story office tower — can sample from a wide range of new public amenities inside the building. At a new multi-level food hall, you can grab breakfast at Do-Rite Donuts and Chicken or spend $19 on a bluefin tuna roll at Sushi San. The Color Factory, an interactive (as in: Instragrammable) art museum, opened up in June, beckoning tourists and locals with chromatic thirst traps. A 75,000-squre-foot conference center hosts group meetings, and weddings are in the works. On the tower’s podium, yoga classes and concerts can be held on a new 30,000-square-foot landscaped roof garden. Office workers in need of an early happy hour can find one in a new bar on the 33rd floor that opens at 3 pm.

Did You Know?
Sears Tower's continued status as the tallest building in the western hemisphere was first published by Since that time, countless newspapers and books -- even the official Website -- have increasingly cited this fact as a popular alternative to the "tallest building in North America."



As of 2023, Sears Tower not only remains the tallest office building in the western hemisphere by roof height, but also the second-largest private office building.

Annually 1.3 million people visit the observation deck alone, making The Big Store the 7th most popular tourist destination in Chicago (Source: Chicago Tribune, Sept 14, 2006). In addition, a recent public poll conducted by the American Institute of Architects, in commemoration of its 150th anniversary, ranked Sears Tower as America's third favourite Chicago architectural landmark.

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Building Technical Data

Official Name:

Willis Tower

Popular Name:

Sears Tower

Street Address:

233 South Wacker Drive

Postal Code:


Time Zone:

U.S. Central Standard Time (-0600 UTC)
U.S. Central Daylight Time (-0500 UTC)

Global Coordinates:

-87°38'11" Longitude
41°52'43" Latitude

Street Boundaries:

Wacker Drive
Franklin Street
Jackson Boulevard
Adams Street
Quincy Street (removed)

Average Occupancy:

10,200 Persons Daily

Average On-Site Traffic:

25,000 Persons Per Day

Model Unveiling

July 27, 1970


August 1970

Steel Erection

June 1971


May 3, 1973

Initial Opening

September 1973

SkyDeck Opening

June 22, 1974


Sears, Roebuck & Co.

Chief Architectural Designer

Bruce Graham, Partner (SOM Chicago)

Principal Structural Engineer

Fazlur R. Khan (SOM Chicago)

Interior Designer


Wind Analysis

Weidlinger Associates

Mechanical Engineer

Jaros, Baum, & Bolles

General Contractor

Diesel Construction (aka Morse-Diesel Inc.)

Electrical Engineer

Jaros, Baum & Bolles, Assoc.


American Bridge Division of US Steel


American Bridge Division of US Steel

Rental Agent

Cushman & Wakefield Inc.

Security Integrator

Johnson Controls, Inc.

Site Area:

~3 Acres

Gross Floor Area:

~4.56 Million Sq Ft

Rentable Floor Area:

~3.81 Million Sq Ft

Parking Facilities:

160-Car Underground Garage (Wacker Drive)
1,010-Car Standalone Garage (Adams Street)

Height Above Grade:

1729-Ft (from Franklin Street entrance)

Occupiable Floor Levels:


Floor Plate Dimensions:

195-Ft x 195-Ft Maximum

Observatory Name:

SkyDeck Chicago

Observatory Levels:


Observatory Elevation:

1,353 Feet

Primary Architectural Style:


Primary Structural System:

Bundled Tube

Construction Materials:

Prefabricated Steel "Christmas Tree" Frame
Concrete and Steel Composite Floor Deck
Steel Truss Floor Joists

Cladding Material:

Bronze-Tinted Vision Glass
Black Anodized Aluminum Spandrel Panels
Black Anodized Aluminum Framing

Foundation Type:

114 Bell Reinforced-Concrete Caissons

Foundation Depth:

65 Feet

AM/FM Radio Transmitters:


NOAA Wx Radio Transmitter:


Analog Television Transmitters:


Digital Television Transmitters:

WGN-DT-19 (WB)

Graphical comparison of Sears Tower to similar skyscrapers.

Recent news headlines about Sears Tower.

Historic news headlines about Sears Tower.

Awards and Acknowledgments:

  • "Distinguished Building Award", AIA, Chicago Chapter (1976)
  • "Award of Excellence", American Institute of Steel Construction (1975)
  • "Best Engineering, High Rise Construction Award", American Iron & Steel Institute (1975)

Visit the official homepage of

Twin Towers Alliance

Watch ABC7 Chicago's realtime Sears Tower skycams.

For those wondering about the title of the site, it is a play on 1001 Arabian Nights. And yes, storeys is an actual English word I chose for its spelling.

Copyright © 1998-2023, Randall E. Krause. Unauthorized reproduction prohibited.
This site is not affiliated with The Blackstone Group nor Sears Brands LLC.
"Sears Tower" and the quadrant-extrusion logotype are trademarks of Randall Krause