Iron Bridges

There are actual samples of the bridge signs from the bridge builders listed in this section. Pictures of the iron bridges are shown with the associated bridge sign. Click on an individual picture to get a bigger view.

You might want to view the King Iron icon first as it has several pages about the bridges, signs, design and locations in Central Illinois. The Clinton, Indiana, Massillon and Wrought Iron sections have the largest amount of bridge signs and related stories.

I intend to add a paragraph about each bridge company. I would appreciate it if you have such information about a listed builder that you could share on this website.

Iron Bridge History

Between 1830 and 1840 iron was first used in the form of beams, mostly for smaller bridges.

Most of the early iron truss bridges were constructed with tubular cast-iron compression members, either cylindrical or octagonal in shape, designed to abut against joint boxes engaging the posts chords, lateral struts and web diagonal members or upon each other with the provision upon one of tie abutting members for connecting the posts, lateral struts and web diagonals. In general, tree lateral bracing diagonals were connected upon the lateral strut members. The abutting joints were designed to facilitate field assembling without the use of flanges and bolts, the connections being formed with integrally cast sleeves, thimbles, tenons, collars or lugs to prevent lateral motion and to insure joint rigidity. The tension members were common ply wrought iron rods, the end connections having loop eyes and pins or upset threads with nuts.

From 1851-61 many iron bridges from 65 to 110 feet spans were built on the western and mountain divisions of the Pennsylvania RR. These Pratt trusses were stiffened with arches, top chords, and posts being of cast iron.

Prior to 1860 the truss types utilized in metal spans were those patented by Square Whipple (1841-46), Wendall Bollman(1852) and Fink (1857) wherein cast iron compression members and wrought iron tension members were selected to fulfill their respective truss functions.

In 1861 rolled wrought-iron sections were first used in the components of truss post members and the ends of flat bars were forged to form heads on tension members.

The first bridge to use rolled wrought-iron shapes in both compression and tension members was manufactured in 1863.

In general, the metal structures built between 1840 and 1870 had cast iron compression members and wrought iron tension members. But it should a1 so be noted that a plate iron superstructure was built in 1846-47 and that the first American bridge having plate girders was fabricated in 1861.

The use of cast iron in railroad bridge construction ended about 1870 and in highway bridges it was continued until about 1880, The use of wrought iron plates, bars and shapes began about 1850 and terminated when the mills discontinued rolling about 1895. The rolling of structural steel for general use was begun in 1884 so that within the transition period the built-up members of structures were frequently made up rather indiscriminately of the two materials.

On August 12, 1875, the Edgar Thompson Steel Works poured from a Bessemer converter its first melt of steel and in 1878 it produced a steel which went in to the construction of the five main river spans of the Glasgow bridge over the Missouri River at Glasgow, Mo.

from "A Record of History and Evolution of Early American Bridges"
by Llewellyn Nathaniel Edwards.University  Press, Orono, Maine. 1959