Roebling first signed on as a surveyor for the Beaver River canal system, launching his career with a string of canal and railroad projects. Aside from writing articles in engineering journals, Roebling designed his own wire cables and started his own company to manufacture them; the John A. Roebling Company was the first wire rope manufacturer in the United States. Gradually gaining fame for his civil engineering, Roebling finally got to build suspension bridges. His first bridge was the Allegheny Suspension Aqueduct in Pittsburgh. The structure, completed in 1845, was the first suspension aqueduct in the world and the first large American suspension bridge that had multiple spans. Furthermore, it was the first suspension structure built with modern cable-spinning techniques—Roebling's own invention. Earlier bridge building techniques involved fabricating the main cables at a factory, transporting them to the bridge site, and then stretching the heavy cables over the gap to erect them over the bridge. Roebling, during his experiments with wire ropes, conceived and patented a new construction method for these main cables. A long line—the traveler rope—formed a loop around two horizontal wheels, one on each side of the gorge. A lightweight wheel, "the traveling wheel," was attached to this line, and a wire threaded around this wheel. Like a belt in a mechanical system, the traveler rope and its wheel moved across the gap as the horizontal wheels turned, pulling the wire along. The traveling wheel effectively hauled two lengths of the same wire (running above and under the traveling wheel) across the gap at a time. The lengths of wire were collected and bound at intervals to form thicker strands, which were later compressed together into the main cables, supporting themselves and later the proportional weight of the bridge as they were formed. The method became the standard for suspension bridge construction, and remained unchanged for many years. In the 20th century, suspension bridges were still built with this pulley winding system, albeit with more sophisticated equipment.