High Steel: The Daring Men Who Built the World's Greatest Skyline (5 page)

In 1883, a practical-minded architect with the ornate name of William LeBaron Jenney began planning the nine-story Home Insurance Building right in the heart of the Loop. Jenney, born in 1832, was one of the older architects in the city. He had employed and mentored many of the young Chicago architects whose reputations would eventually surpass his own, including Daniel Burnham
and Louis Sullivan. He was respected and well liked—a natural “bon vivant,” as Sullivan described him—but nobody thought much of his aesthetic judgment. Jenney had spent the Civil War as an engineer for Ulysses S. Grant, and later for William Tecumseh Sherman, rebuilding bridges for the invading Union army. He thought like an engineer. Pragmatics came before aesthetics, calculation before decoration.

As Jenney planned the building, he faced an architectural conundrum. On one hand, the building, to pay for itself, would have to be tall, at least nine stories. On the other hand, the president of the Home Insurance Company, J. J. Martin, insisted that the building have numerous windows to permit light and fresh air into offices. A normal masonry high-rise was out of the question. “How are you going to manage it?” wondered Martin. Jenney replied that he was going to go home and think about it.

In one version of the story, almost certainly apocryphal, Jenney arrived home, deep in thought, and came upon his wife reading a book. As she closed her book and set it atop a birdcage, Jenney’s eyes narrowed on the birdcage. Seeing how the thin rods of the cage so effortlessly bore the weight of the book, he was struck by a vision of a building constructed like a cage, in which the weight of the building is removed from the walls and placed on a metal frame, and in which the walls are no more important structurally than the blanket laid over a birdcage at night. Eureka!

A hapless young Minneapolis architect named L. S. Buffington had a more sinister explanation for Jenney’s epiphany: he believed that Jenney swiped his idea. Buffington had been dreaming of tall skeleton-frame buildings (he called them “cloud sketchers”) as early as 1880 and had written and spoken of them well before the Home Insurance Building came into existence, although he never actually built one. As for where he got
his
ideas, he credited the French architect Viollet-le-Duc, who years earlier had envisioned a building remarkably like a skeleton-frame skyscraper: “A practical architect
might not unnaturally conceive the idea of erecting a vast edifice whose frame should be entirely of iron, enclosing that frame and preserving it by means of a casing of stone.”

Actually, Jenney’s plan for the Home Insurance Building was neither an act of thievery nor a leap of genius. It was a simple step of logic. Iron columns and beams had been deployed architecturally since the middle of the nineteenth century, when cast-iron buildings first began to rise in New York City. In masonry buildings, cast-iron columns had been used to add strength to walls and piers, and wrought-iron beams had long served as lintels and girders. So the idea of using iron framing to support buildings was not new. What
was
new was the idea of supporting the building
entirely
with iron framing.

The idea owed something to earlier architecture, but it owed an even larger debt, often overlooked in histories of skyscrapers, to the railroad bridges of nineteenth-century America. Jenney’s experience in the Civil War made him well acquainted with bridge-building techniques and almost certainly influenced his architecture. Bradford Gilbert, that fearless designer of New York’s Tower Building, referred to his own metal-frame design as “an iron bridge truss stood on end.” When steel-frame skyscrapers became common late in the century, it was bridge companies that fabricated the steel and oversaw their erection. Bridges, with a metaphorical aptness worthy of bad poetry, were what you crossed on your way to the modern city.

FLYING TRAPEZOIDS

“It is a notorious fact that there is no country of the world which is more in need of good and permanent Bridges than the United States of America,” wrote the American bridge builder Thomas Pope in 1810. Just four years after Lewis and Clark returned from their failed hunt for a water route across the continent, Pope foresaw that the
future of the country depended not on navigating rivers but on spanning them. “Extended along an immense line of coast on which abound rivers, creeks and swamps, it is impossible that any physical union of the country can really take place until the labours of the architect and mechanic shall have more perfectly done away the inconvenience arising from the intervention of waters.”

Nineteenth-century American bridge builders built more bridges than any country in the world. Before the end of the century, over 200,000 bridges would be erected in the United States, some 3,000 miles of bridge in all. Acknowledged masterpieces like the Brooklyn Bridge in New York and the Eads Bridge in St. Louis notwithstanding, the great majority of nineteenth-century American bridges were unlovely, workmanlike truss bridges, or what engineer Thomas Curtis-Clark referred to, in 1869, as “skeleton girder” bridges (anticipating the term for metal-frame building by about 30 years). A truss was essentially a brace, usually trapezoidal, that ran along each side of the bridge span to prevent it from sagging or collapsing. Each side of the truss was comprised of a top chord and a bottom chord—the principal horizontal girders—and, between the two, a lattice of diagonal cables or bars. The genius of a good truss was that it gave ample support without adding much weight. This was critical. The more something weighs the stronger it needs to be simply to hold itself up and—not incidentally—the more it costs to build.

As with most engineering, bridge building was the art of doing more with less, and a good truss combined strength with economy. But strength was difficult for early bridge builders to calculate. Unlike buildings, in which strains, absent earthquakes, were fairly constant and predictable (gravity pulling down and wind pushing sideways), even the simplest bridge faced complex strains in keeping its own dead load aloft. Then came the sudden intense impact of the live load—a 35-ton locomotive, for instance, trailed by hundreds of clattering tons of freight—and the bridge jiggled and danced on its bolts and pins, its iron pulled and pressed and wrenched, and then a
few moments later it was all over. The live load was off to torture another bridge, and the dead load recovered, unbent, and attempted to resume its pre-assaulted state. Every time this happened, it became a little more arthritic, a little less like its old springy self. And then, one day, perhaps, it collapsed.

Bridges collapsed frequently in the late nineteenth century, 25 times a year on average in the 1870s and 1880s. Occasionally, a bridge collapsed spectacularly and with great loss of life, as occurred one snowy December night in 1876. Two locomotives, traveling front to back and trailed by 11 railroad cars, slowly started across a 13-year-old wrought-iron bridge in Ashtabula, Ohio. The first locomotive had just made it safely across when the bridge fell. The second locomotive and all 11 cars fell with it into the deep gorge below. Ninety-two people died, making Ashtabula the worst American train disaster of the century.

When a bridge fell, engineers flocked to its mangled remains, eager to learn what had gone wrong so they could avoid the fatal flaw in their own bridges. With every disaster they learned what worked and what failed. What were the tolerances of cast or wrought iron? Which arrangements of chords and diagonals gave strength to a truss and which did not? The bridges schooled American engineers, providing them an opportunity to experiment with new structural forms and to gauge the strength of materials, like iron, that would play such an important role in the development of skyscrapers.

Iron was still something of a mystery metal when the first iron bridges began going up in the middle of the nineteenth century. The material had been in use in various forms for thousands of years but until this moment nobody had ever asked much of it structurally. The oldest form of iron is wrought, which humans began using in substantial quantity around 1200 B.C. Wrought iron is the reduction of iron ore heated at very high temperatures. Cast iron came later, in
the fourteenth century. The main difference between wrought and cast iron is the amount of carbon that binds with the iron during smelting. Wrought iron has very little carbon; cast iron has a great deal of it. Wrought iron is softer, more pliable and flexible. Cast iron is hard and brittle; it is easily cast in shapes—hence its name and prevalence as an ornamental metal—and bears up well under great weight. Under the wrong conditions, though, cast iron buckles and breaks. In the parlance of engineers, wrought iron performs best under
tension
—as, for instance, a floor beam—while cast iron performs best under
compression
, as a column. Nobody really understood these distinctions when builders began putting up iron bridges. And when the transition to steel began in the 1870s, nobody understood much about it as structural material either.

Steel had been around almost as long as iron. The
Oxford English Dictionary
cites a reference to steel—“style”—in
Beowulf
, from the year 725. Chaucer used the word, which he wrote as “steell,” in 1380, though it’s not clear that his steell was the same thing as our steel. The word generally connoted a superior form of wrought iron into which some carbon had seeped during the smelting process to give the iron more hardness. Steel’s carbon content, about 1.5 percent, is higher than wrought iron’s but lower than cast iron’s.

Most early structural steel was crucible steel, a laboriously manufactured high-carbon version. James Buchanan Eads insisted on crucible steel in parts of his great bridge over the Mississippi River at St. Louis, completed in 1874. Eads’s steel supplier was the Keystone Bridge Company, a subsidiary of Andrew Carnegie’s burgeoning empire. Carnegie still had doubts about the future of the product that would transform him from a rich Pittsburgh businessman into one of the wealthiest men in the world. But in 1868, he took a trip to Britain and witnessed a demonstration of a new invention called a Bessemer Converter. The trick to economically turning molten “pig” iron into steel, an Englishman named Henry Bessemer had discovered, was to blow air through it as it heated. The air burned off
excess carbon 10 times faster than any previous method and used less fuel to do it. For the first time in history, steel could be manufactured quickly, cheaply, and in vast quantities. Carnegie needed no more convincing.

Steel was slow to win acceptance as a sound or practical structural material; early on it was used mainly for rails on railroad tracks. But gradually engineers came to recognize its superiority to both wrought and cast iron. Steel combined the best of both metals—the flexibility of wrought iron and the brute bearing strength of cast iron—and was at least 20 percent stronger than either. New methods of production would soon make it a good deal stronger.

Like iron, steel first proved itself on bridges. The first all-steel bridge went up in 1879 in Glasgow, Missouri. That same year, Washington Roebling changed the specifications for the floor beams and trusses of the Brooklyn Bridge from wrought iron to steel. (Ten years earlier, his father, John Roebling, had decided to use steel in the bridge’s suspension cables.) Steel’s migration from bridges to buildings was a simple step, pushed by the hand of Andrew Carnegie. The market for steel rails was drying up in the late nineteenth century. Carnegie, with his extraordinary nose for progress, anticipated skyscrapers as a new market for his Bessemer Converters before most people had any idea what a skyscraper was.

William LeBaron Jenney once again played the role of pioneer. His plan for the Home Insurance Building originally called for a structure of cast-iron columns and wrought-iron beams. But after ground broke on May 1, 1884, Jenney received a letter from Carnegie, Phipps & Co. inviting him to try its new steel beams. Jenney agreed to place steel in the top three floors, marking the first use of structural steel in architecture. When the Home Insurance Building topped out in the winter of 1885, the steel skeleton-frame skyscraper—all nine stories of it—was born.

CIRCUS ACTS

As iron and steel came of age on nineteenth-century bridges, so too did the trade of ironwork. Long before the men who practiced it called themselves ironworkers, they were “bridgemen,” and bridgemen they remained long after they turned their skills from skeleton-girder bridges to steel-frame buildings. The two types of structure were so similar that the skills and constitution a man required to build one applied equally well to building the other.

Early bridgemen lived hard itinerant lives. The bridges they built were often in the middle of nowhere, or near some no-luck town looking to the railroad for salvation. They camped at the site or, if they were fortunate, found a room in a nearby boarding house. The work itself was difficult and perilous, but also sometimes thrilling. From these remote towns the bridgemen frequently picked up starry-eyed farm boys as new recruits. “Here is how we get ’em,” an engineer explained some years later. “A big railroad bridge is being built over a river. The boy from the farm comes to watch it. He sees the men climbing out over the water, using ropes for staircases, taking all kinds of daredevil risks. And pretty soon his jaws fall open, and he says to himself that this here game beats the circus all to hollow…. He watches his chance; he gets out there himself, learns how to tie ropes and sit on air. In a few months, he is one of the gang. And then good-bye to the farm. It’s the roving life after that, from Maine to the Rockies.”

The bridges were usually prefabricated in shops, then shipped in sections to the site for assembly. The bridgemen fastened the sections by pounding long iron “pins” through matched eyeholes, then bolting them tight. It was called the “pin-connection method” or simply “the American method,” and with it American bridgemen could raise a bridge faster than anyone on earth, often within a matter of days. Speed mattered. It mattered because the railway was spreading over the country like wildfire, making the demand for
bridges relentless. It mattered, too, because truss bridges were generally erected over rivers. A temporary wooden scaffold, or “falsework,” would be driven into the river’s bed to take the weight of the iron until the bridge’s superstructure was assembled and self-supporting. Compared to the lazy old rivers of England, America’s waterways tended toward the violent and the unpredictable. Bridgemen lived in constant fear of ice flows or “freshets” suddenly gushing down from mountain melts and whisking away the falsework and the bridge and, potentially, the bridgemen themselves.