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The Sky's the Limit!

The anniversary of the Sears Tower "topping out" is the perfect time to explore some of the world's tallest buildings! Skyscrapers are a great curriculum topic -- with lots of concepts and numbers for students to wrap their minds around! Included: Activities across the curriculum!

"She towers so high, just scraping the sky, she's the tallest rock."

Twenty-five years ago May 3, electrical workers who had formed a band performed that opening line of a song penned for a very special occasion: the "topping out" of the Sears Tower. As television cameras rolled, a crowd of more than 1,000 people celebrated on the day when the last beam -- signed by more than 12,000 construction workers, Sears employees, and other Chicagoans -- was hoisted to the top of the world's tallest building.

At 1,454 feet, the roof of the Sears Tower stood 86 feet over the world's next tallest building, New York's World Trade Center, completed just one year earlier. The 110 floors of the now-tallest Sears Tower combined to provide 4.5 million square feet of space, more floor space than any other building in the world, except the Pentagon.

It would be 1974 before the building was officially completed, but in the world of high-rise construction, topping-out is often the most celebrated point in the project, equal to a climber reaching the top of a mountain. And this wasn't just any mountain -- it was the highest urban mountain of its time.

The unprecedented engineering feat was designed by architects Skidmore, Owings and Merrill, a firm already well-known for another towering accomplishment, the John Hancock Center in Chicago. The firm designed the building using a technique devised by structural engineer Fazlur Khan, who discovered that a building constructed of a series of tubes would be lighter and stronger than a building constructed with a traditional steel skeleton.

The Sears Tower uses nine such tubes, with all the tubes intact to the 50th floor, where the first "setback" occurs -- where the face of the building is set back from the face of the floor below it. Setbacks are introduced at the 66th floor and at the 90th floor, so that the top 20 floors are constructed of just two tubes. The result is both aesthetically pleasing and structurally sound.

With the construction of the monumental building, though, came challenges of equal proportions -- and lots of concepts and numbers for students to wrap their minds around!


For example, as the structure grew taller, it became inconvenient and impractical for workers to trek all the way down to street level for lunchtime and coffee breaks. Can you imagine how long it would take to go down 100 floors in a slow moving construction elevator? How do your students suppose workers dealt with the problem? (Here's how the folks at Sears Tower handled it: Mobile catering kitchens were installed on the 33rd and 66th floors. Let's hope they had bathrooms there, too!)

One of the major problems for designers -- wind -- became a major problem for workers, too. The workers regularly scaled ropes and narrow six-inch beams to do their jobs. But at more than 1,000 feet in the air, the wind was often so strong that they couldn't stand up in it! Appropriately enough for "The Windy City," wind was the only thing that ever caused construction delays on the tower.


Ask your students to imagine the windiest, blow-you-down day they've ever experienced. Now imagine standing on a beam or a rope 1,000 feet in the air -- and then holding heavy tools to rivet and pound things together! How do they suppose the workers kept from falling off? Is this perhaps the most dangerous job ever? (If not, what is?) Why do people do it? Would your students do it? A fascinating first-person narrative on ironworkers, with lots of photos, is Steel Beams & Iron Men by Mike Cherry, a writer and a former ironworker. (Be forewarned, though, that the book contains some mild four-letter usage, "hell" and "damn," that some students and parents might find offensive.)


Within the Sears Tower are 25 miles of plumbing, 1,500 miles of electric wiring and 80 miles of elevator cable. Can you imagine 1,500 miles of electric wiring? Amazing! Get out the maps: Start at the Sears Tower and unravel it. Where would it stretch to?

The Sears Tower is in Chicago, a city that while not exceedingly polluted, does have its share of urban grime. With 110 stories of 16,000 windows, that's a lot of Windex! Any ideas on how the building is kept clean? (The way it works: Six automatic window-washing machines run on tracks on the outside of the building, spraying the building with water and detergent, brushing the windows and the aluminum skin, and then vacuuming up the water, filtering and reusing the water as it goes.)


The 1,454-foot Sears Tower remained the world's tallest building for 23 years, when it was surpassed by the 1,483-foot tall Petronas Twin Towers in the Malaysian capital city Kuala Lumpur, although there is some debate (mostly sparked by people who live in Chicago!) about which building is actually the taller of the two. Although the Petronas Towers are higher, thanks to their 246-foot spires, the towers' 88 occupied floors, which rise to 1,229 feet, fall far short of the Sear Towers 110 stories, which rise to 1,431 feet.

The squabbling likely will be put to an end, soon, however, as even taller buildings appear on the horizon. Construction is to begin in August on the 1,507-foot World Financial Center in Shanghai, China. The proposed Millennium Tower in Tokyo, if built, will easily claim the world's tallest title at 2,755 feet, and Skidmore, Owings & Merrill are still in the tall-building business, too, with a design for the 2,100-foot Russia Tower in Moscow.

How tall can or should a skyscraper be? And do we still need them? Given corporate downsizing and an increase in telecommuting, most corporations need less office space, not more. Are skyscrapers becoming dinosaurs? (Now there's a point to ponder: We know the difficulty in putting up a skyscraper -- can you imagine trying to take one down?) No one has these answers quite yet, but one thing is certain: As long as there is a tallest building, there will be someone, somewhere, who wants to build one even taller!

And in the meantime, there's a tower of opportunity for learning. Here are some ideas for the classroom:


Get out the graph paper and colored markers to chart the world's top 10 tallest buildings (for right now, anyway!), according to the Council on Tall Buildings and Urban Habitat:

  1. Petronas Tower 1, Kuala Lumpur, 1,483 ft.
  2. Petronas Tower 2, Kuala Lumpur, 1,483 ft.
  3. Sears Tower, Chicago, 1450 ft.
  4. Jin Mao Building, Shanghai, 1,380 ft.
  5. World Trade Center, One, New York, 1,368 ft.
  6. World Trade Center, Two, New York, 1,362 ft.
  7. Empire State Building, New York, 1,250 ft.
  8. Central Plaza, Hong Kong, 1,227 ft.
  9. Bank of China Tower, Hong Kong, 1,209 ft.
  10. T & C Tower, Kaoshiung, 1,140 ft.

How about letting the number of stories tell the story?

  1. Sears Tower in Chicago: 110
  2. World Trade Center in New York: 110
  3. Empire State Building in New York: 102
  4. Jin Mao Building in Shanghai, China: 88
  5. Petronas Twin Towers in Kuala Lumpur: 88
  6. T & C Tower in Kaoshiung, Taiwan: 85
  7. Standard Oil in Chicago: 80
  8. Chrysler Building in New York: 79
  9. Central Plaza in Hong Kong: 78
  10. First Canadian Place in Toronto: 72


Here are some other fascinating facts for charts, graphs, and general mind-boggling, from The Skyscraper Book by James Cross Giblin (Thomas Y. Crowell, 1981):

  • The 60-story Woolworth Building in New York, constructed in 1913, required 17 million bricks, 7,500 tons of terra cotta, 53,000 pounds of bronze and iron hardware, and 87 miles of electric wiring.
  • The Terminal Tower in Cleveland has its foundation on bedrock, 130 feet below the level of nearby Lake Erie. The tower includes 17,800 tons of steel and 7.5 miles of electric wire.
  • The Empire State Building in New York required 60 miles of water pipe and over 3,500 miles of telephone and telegraph wire. And from the observation decks, rain and snow can sometimes be seen falling up instead of down because of wind patterns around the building!
  • The World Trade Center in New York (built in 1970-71), used enough concrete to lay a sidewalk five feet wide from New York City to Washington, D.C. The electrical wiring for the twin towers would have reached from New York to Mexico! (Get out those maps again -- how many miles is it?) Over a million cubic yards of earth and rock were excavated to make way for the World Trade Center. The excavated material was placed in the Hudson River, creating 23.5 acres of new land.
  • There are 42,614 panes of reflective glass in the IDS Center in Minneapolis (built in 1972), enough to provide two pairs of sunglasses for each resident of Minnesota and one pair for each resident of North Dakota and South Dakota.
  • The Sears Tower contains enough concrete to build an eight-lane highway five miles long (and a two-lane highway would be. . . ?). If laid out on the ground, the black aluminum skin of the tower would cover 28 acres (or how much of Disney World?)

Article by Colleen Newquist
Education World®
Copyright © 1998 Education World

Related Resources


Related Sites


  • Sears Tower Overview Slightly outdated (still calls Sears "world's tallest") but has useful facts and figures on the Sears Tower.
  • Who's the Tallest of Them All? An argument in favor of the Sears Tower retaining its "world's tallest building" stature -- and a chance to vote on it!
  • Jeff Herzer's World's Tallest Buildings Page Put together by a journalist with a passion for the world's tallest buildings (the two dozen on the planet that are over 1,000 feet tall). This site includes a wealth of information on buildings under construction, proposed projects and buildings never built, as well as a photo gallery and an online magazine. His enthusiasm is contagious!
  • Hans Netten's The High Rise Pages Another enthusiast's site chock full of information. (Warning: Graphics-heavy; may be slow loading.) Contains 164 links to information on high-rises in 23 countries. He also goes beyond buildings to give information on the tallest towers, churches, flagpoles, and monuments in the world, among a mountain of other information.
  • Council on Tall Buildings and Urban Habitat Contains fantastic searchable database with information on thousands of high-rise buildings. Can search 100 tallest buildings in the world (although non-members are given only the top 10); search for specific buildings according to name, height, date, location; or search for professional specialists.
  • International Superstructure Mensuration Alliance A site that bills itself as "advancing public appreciation of tall building principles and technologies." Or, alternatively, the first and foremost Web site providing answers to that question of questions: "Just what is a tall building?"
  • Great Structures of the World Photographs and information on "structures that push the limits of engineering and architecture."
  • The Skyscrapers Page A collection of links to pages on some of the world's best-known skyscrapers and proposed projects. (Frustration warning: Not all the links were working.)
  • Hise-Rise Buildings in the World A graph of the construction (height vs. time and continent) of high-rise buildings in North America, Asia, and Europe.
  • High-Rise Buildings in the World (From the Swedish Institute of Steel Construction) Contains a graph of some of the world's tallest buildings and towers, plus a chart of information on numerous tall structures around the world.
  • Tall Buildings Rankings Another list of the world's tallest, including two not yet completed.
  • New York Skyscrapers Although not the birthplace of the skyscraper (that claim belongs to Chicago), New York is nonetheless synonymous with skyscrapers. This page offers information along with Webcam views from some buildings.