John Augustus Roebling

Born June 12, 1806

Mühlhausen, Germany

Died July 22, 1869

Brooklyn, New York

Engineer and bridge designer whose most famous work is New York City's Brooklyn Bridge

"As a great work of art and as a successful specimen of advanced bridge engineering, [the Brooklyn Bridge] will forever testify to the energy, enterprise, and wealth of that community…."

C arving a European-style country out of the North American continent in the nineteenth century was a mammoth undertaking. A key element was building transportation routes across the wild, uncharted territory. Bridges were a vital, if often overlooked, element in both water and surface transportation. John Augustus Roebling, an immigrant from Germany, made two major contributions to the developing nation's transportation: He developed steel ropes, or cables, and he developed the nation's first suspension bridges, which could span longer distances than could bridges made with other technologies.

The story of how Roebling came to be America's first major bridge builder is in most respects typical of how the United States attracted bright young people during the nineteenth century with a promise of a better life than they could expect in Europe, and how in turn these immigrants rewarded their adopted country with talent and innovation that made the miracle of rapid development possible.

Starting out from Germany

After England and Ireland, Germany was the largest contributor of immigrants to the United States in the new country's first century. Unlike the Irish, who came in an enormous group after the failure of the potato crop in the late 1840s, Germans tended to come in a steady stream. Roebling was typical.

Born in Mühlhausen, Germany, in 1806, the youngest son of Christoph Roebling and his wife Friederike Mueller, John Augustus Roebling was educated in public schools and by tutors to prepare him to attend the Royal Polytechnic Institute in Berlin. (Polytechnic schools prepare students for careers in engineering, architecture, and other fields requiring advanced knowledge of mathematics and physics.) Roebling's mother was said to insist that her children receive a good education, even if it meant sacrificing some of her own private needs. At the Polytechnic Institute, Roebling studied architecture, bridge building, and hydraulics (the science of pumps), as well as languages and philosophy. When he graduated in 1826, he took a government job helping to build roads.

Roebling was not happy with his prospects as a civil engineer (an engineer who designs public projects, like roads) in Germany. He was highly interested in bridges, especially suspension bridges, but his government job did not seem to offer a chance for innovation and challenge. On the other hand, the 1820s and 1830s were a time when Germans were beginning to immigrate to the United States in significant numbers. The country had begun its steady expansion westward, made possible by the defeat of Native American tribes defending their traditional territory and way of life. The market in Europe for American agricultural products was growing, creating a demand for new farms in the United States. It was also a period of intense construction of the new nation's infrastructure, the set of public works like roads and canals that make it possible to travel and carry goods to and from markets.

Roebling planned carefully with his brother Karl. They calculated that their best opportunity lay in farming, and in the spring of 1831, the two brothers set out for Philadelphia, Pennsylvania. They had ruled out settling in the South because both opposed slavery, and they realized that substantial numbers of German emigrants were settling in Pennsylvania.

Traveling by sailing ship, the Roebling brothers arrived in Philadelphia on August 6, 1831. They soon left Philadelphia and headed for Pittsburgh. The early 1830s marked the high point of canals in the United States—essentially man-made rivers along which flat-bottomed boats were pulled by horses or mules walking alongside the canal. When the Pennsylvania Canal, spanning the state from east to west, reached the Allegheny Mountains in the center of the state, the canal boats had to be taken out of the water and placed in special wagons that could be pulled along a smooth surface called the Allegheny Portage Railroad. The railroad, which was nothing like modern railroads, was nevertheless a key link in the Pennsylvania canal system. The railroad for the boats demonstrated the principal drawback of canals: they needed to be flat (so that the water in these shallow rivers did not flow out). Canals were poorly suited for mountains or hilly terrain.

Bridge-Building Basics

In building a structure across a space, such as a river, a highway, or a mountainous ravine, there are several different sets of problems. The basic issue is to build the roadbed of the bridge (the part that bears the weight of whatever is to use the bridge, such as cars) so that it does not crack and break into two. The second basic issue is building the roadbed long enough to stretch across the river, or body of water, or whatever the bridge is crossing. The distance across a bridge is called the span.

There are three basic types of bridges. The first type is an arch. Usually made of bricks or stones, an arch is extremely strong but can cover only a limited distance. An arch comprises the ends of the bridge, which look like columns, with an arch between them. The arch itself is usually made of bricks, cut so that they form a half-circle. When weight is put on the roadbed, the bricks are, in effect, squeezed together even more tightly, so that the arch supports the span. Arches are usually the shortest bridges.

The second type of bridge is a truss. A truss is, in its essence, a strong beam that goes across the span. In order to prevent having the beam sag in the middle, engineers actually use two beams, an upper and a lower one, in between which are supports arranged as triangles. The triangles keep the top and bottom beam separated and also enable the beams to bear more weight. A simpler version of a truss is the I-beam, a long piece of metal with two flat, wide parts on top and bottom and a thin vertical piece in the middle. Looked at from one end, an Ibeam looks like a capital I.

The third type of bridge is the suspension bridge. In this case, a long, strong cable is stretched from shore to shore, across the tops of two tall towers, forming a shape like a capital M. The V shape in the middle of the M is formed by the cable, while the vertical strokes on the M are the two towers. Normally, the cables extend beyond the towers and are attached to a large anchor buried into the ground at either end. Vertical bars are hung from the cables and attached to the upper surface of the roadbed. To make the roadbed even stronger, a truss-type bridge is constructed. In a suspension bridge, the roadway basically hangs from the cables.

The advantage of suspension bridges is that the cables between the towers can be quite long. If they are thick enough and strong enough, they can hold up the roadway. A disadvantage is that suspension bridges may sway in a strong wind, putting stress on the structure and possibly causing it to fall.

The importance of the cables was well understood by John Roebling, America's first master suspension-bridge builder, since he pioneered the so-called wire rope.

Twenty-five miles from Pittsburgh, the two brothers bought a significant plot of land, about 7,000 acres, near a community of other German immigrants. The town was named Germania, but later changed its name to Saxonburg. Other Germans from Mühlhausen, encouraged by letters from the Roebling brothers, also moved to Saxonburg. In 1837, Roebling married Johanna Herting, the daughter of one of those immigrants.

After six years, however, Roebling's farming venture was not proving to be a success, largely because the land he and his brother had purchased was not suited for the purpose. On top of this, Roebling missed engineering, the work he had been trained for and enjoyed.

Wire rope

In 1838, a year after his marriage, Roebling traveled to Harrisburg, the state capital, and applied for a job as an engineer for the state government. He also became an American citizen in the same year. Employed by the state of Pennsylvania, Roebling worked on a variety of projects: designing more canals, building dams on the Beaver River, and surveying a route for a railroad across the Alleghenies.

The Allegheny Portage Railroad provided Roebling with his first major success. The route of the railroad went up and down the steep hills of the Alleghenies. A complex system of thick ropes was used to haul the canal boat carriages up and down the hills. These ropes, which were about 3 inches thick, were made from hemp, a plant whose fibers were especially suited to manufacturing woven ropes. The ropes tended to fray, which meant they had to be replaced often.

Roebling envisioned a new type of rope, made of twisted wire. The so-called wire rope would resist fraying, and could be made of a smaller diameter while providing superior strength. The thinner wire ropes would be easier to handle, as well as lasting longer.

Roebling presented his idea for "wire rope" to the state officials in charge of the Pennsylvania canal and, after a delay, convinced the state to try his idea. Roebling returned to Saxonburg where he designed machinery to manufacture the rope and set up a factory. Ironically, Roebling's invention came just at the end of the era of using canals, as railroads using steam engines and running on iron tracks replaced the artificial waterways. To Roebling, however, it did not make a difference. His wire rope found many other markets where stronger, smaller, and longer-lasting cables were used to replace hemp ropes. After a few years operating his factory in Saxonburg, Roebling moved his operation to Trenton, New Jersey, where it remained a family-owned business for generations.

Back to bridges

While manufacturing wire rope provided a comfortable living for Roebling, it was not his first love. Even while operating his factory, Roebling had been active in designing structures. From 1844 to 1850, Roebling built several aqueducts to carry water along the Pennsylvania Canal. Aqueducts are structures designed to carry water; in the case of the Pennsylvania Canal, the aqueducts were the equivalent of bridges, letting the canal flow over gorges or ravines. Between 1844 and 1850, Roebling designed and directed the building of at least six canal aqueducts.

In 1846, Roebling also designed the Smithfield Street Bridge across the Monongahela River in Pittsburgh. Five years

later, Roebling designed a bridge over the Niagara River in Niagara Falls, New York. Roebling's specialty was suspension bridges, or suspension aqueducts, a form of bridge that can span much greater distances than other forms of bridges (see box).

In 1867, Roebling, joined by his son Washington Roebling (1837–1926), launched their biggest and most famous project: a bridge connecting two parts of New York City, Manhattan Island on the west and Brooklyn on the east. (Brooklyn, once a city entirely separate from Manhattan but now part of New York City, is situated on the western end of Long Island.) The bridge needed to be high enough to allow ships to pass underneath.

Roebling had first proposed building a bridge between Manhattan and Brooklyn in June 1857. It took a decade before the project was approved and Roebling was named chief engineer. It took two more years for final plans to be made and approved. But before construction could actually begin, Roebling's foot was mashed by a ferry boat while he was standing on a pier, making observations on the bridge site. Roebling was taken to his son's home in Brooklyn and several injured toes were amputated. Although serious, the injury was not thought to be life threatening. But a few days later, the wound became infected. In an age before antibiotics, or drugs that kill the microorganisms that cause infection, Roebling died three weeks after the accident, never seeing the world-famous bridge that is associated with his name.

Roebling's son Washington, who had worked as his assistant, took over. The statistics of the Brooklyn Bridge give a flavor for the size of the project. The total length of the bridge is over a mile—5,989 feet; the distance between the towers is 3,460 feet, a record distance when it was built. The roadbed is 85 feet wide. Four huge cables stretch from each shore, over the tops of two towers. Each cable is 15¾ inches in diameter and 3,578 feet long. The towers are each 276 feet above the surface of the river. The towers were anchored in bedrock, the thick rock that lies under the bed of the river. The foundation of the east tower is 44½ feet under the surface of the water; the west tower, near Manhattan, is 78½ feet below the surface of the water. The roadway is 119 feet above the water at high tide, enough for both steamships and sailing vessels to pass beneath. The project took fifteen years to complete; it opened on May 24, 1883.

—James L. Outman

For More Information

Books

Kranakis, Eda. Constructing a Bridge: An Exploration of Engineering Culture, Design, and Research in Nineteenth-Century France and America. Cambridge, MA: MIT Press, 1997.

McCullough, David G. The Great Bridge. New York: Simon & Schuster, 1972. Reprint, 2001.

Schuyler, Hamilton. The Roeblings: A Century of Engineers, Bridge-Builders, and Industrialists. Princeton, NJ: Princeton University Press, 1931. Reprint, 1972.

Steinman, D.B. The Builders of the Bridge. New York: Harcourt, Brace, 1945. Reprint, New York: Arno Press, 1972.

Veglahn, Nancy. The Spider of Brooklyn Heights. New York: Scribner, 1967.

Periodicals

Birdsall, Blair. "The Brooklyn Bridge at 100." Technology Review (April 1983): p. 60.

Hammill, Pete. "The Glory of the Brooklyn Bridge." New York (May 30, 1983): p. 27.

McCullough, David. "The Great Bridge and the American Imagination." New York Times Magazine (March 27, 1983): p. 28.

Wohleber, Curt. "The Bridging of America: The Roebling Saga." American Heritage (April 1991): p. 46.

Web Sites

"Brooklyn Bridge." Great Buildings Online. Basic facts about the Brooklyn Bridge. http://www.greatbuildings.com/buildings/Brooklyn_Bridge.html (accessed on March 24, 2004).

John A. Roebling's Sons Co. Online History Archive.http://www.inventionfactory.com/history/main.html (accessed on March 24, 2004).