In the United States of America, some of the finest stone arch bridges built in the country were erected by railroads. Though sometimes, such as during the initial construction of the Transcontinental Railroad, quick and cheap bridges were the name of the game, many railroads opted for stone arch bridges. Stone had the advantage of permanence, and strength. Iron truss bridges were also quite popular on railroads, but, as loads increased, iron truss bridges regularly proved obsolete and dangerous, while the stone arch bridges remained serviceable. Some railroads, such as the Pennsylvania Railroad, ended up building numerous stone arch bridges due to their longevity even when iron truss bridges were generally popular. These Pennsylvania Railroad stone bridges were largely built in remote areas, where regular maintenance was not practical. A famous railroad stone bridge is the enormous stone bridge over the Mississippi at Minneapolis. This bridge, known simply as the Stone Arch Bridge, was erected under railroad tycoon James Hill’s purview.
The original plan was to build an iron truss bridge at the site of the Stone Arch Bridge. Stone was used instead due to its much better durability and permanence. The structure took approximately two years to complete.
Characteristics of Railroad Stone Bridges
Railroad stone bridges invariably were built with premium construction techniques. The stone were precisely cut and Roman arches were preferred. These bridges were not made with cheap, quick workmanship, but were built to last.
While the more minor stone bridges were often built with local stone, some of the major structures used imported stone, preferably granite at that. Benjamin Latrobe of B&O Railroad fame was especially keen on building premium-quality bridges that would not become obsolete, and therefore favored granite heavily, even though these bridges were quite expensive to erect. Though the initial investment on the B&O Railroad bridges was massive, many of these structures remain in use, proving their long-term worth. Many railroads, with a long-term view, ended up wanting the best, so they built with stone. And, it would seem, their investments in stone were well made. After all, there are actually quite a few railroad stone arch bridges that are still being used, and invariably the abandoned railroad stone bridges were closed due to abandonment of the line, as opposed to structural problems. Ranging from culverts to breathtaking viaducts, the numerous railroad stone bridges still in use carry loads many times greater than those for which they were originally intended.
Stone Arch Bridges 