The Calhoun Street Bridge

Calhoun Street Bridge

Description

The Calhoun Street "Iron" Bridge, opened in 1885, still stands and is used today. The bridge was listed on the National Register of Historic Places in 1975. Portions of the content of this web page were adapted from a copy of the original nomination document. [1] Adaptation copyright © 2009, The Gombach Group.

The Calhoun Street Bridge is 1,280 feet long consisting of seven pratt trusses of nine panels 20' x 26' deep. Compression members are the famous four segment Phoenix column and the major tension members are wrought with rectangular cross sections. Secondary braces in the portals add a decorative touch.

The abutments and six piers are of rough stone construction except on the upstream ice breaker edge which utilized cut-block.

The superstructure was fabricated by the Phoenix Bridge Company of Phoenixville, Pennsylvania. Erection was apparently by the Trenton City Bridge Company, F.C. Larvthorpt, Consulting Engineer. The bridge was completed in 1885.

The bridge today [1975] is in good condition and has suffered the usual modifications. The wooden deck has been replaced by a steel lattice. The down river sidewalk has been replaced with hangers for telephone cables. At the portals, structures have been added to support signs and to limit the size of vehicles using the structure. Otherwise, the bridge is much the same as when constructed.

• Opened to traffic in 1860, the City Bridge was constructed entirely of wood
• Destroyed by fire in 1884
• Phoenixville Bridge Company built the replacement bridge with 83 workmen in 60 days
• 7-span, wrought iron, pin-connected Pratt Truss
• 18'6" wide roadway
• 6' sidewalk cantilevered outside the upstream truss (originally had additional sidewalk on downstream side)

Significance

Previous to the Civil War, Wendel Bollman, engineer for the Baltimore and Ohio Railroad had designed a type of rolled wrought iron hollow column for use in bridge trusses. He apparently contacted Samuel Reeves of the Phoenix Iron Works, Phoenixville, PA, in an effort to have the iron rolled to his specifications. Exactly what transpired between the two men is not known, but Reeves patented the round column made up of rolled, semi-circular sections riveted together. After this, this type of column was known as the Phoenix Column.

From about 1867 or 1870 to the late 19th century, this was the most popular bridge construction in the United States. The Phoenix Column could be used for any size bridge, from multi-span complexes to smaller single spans. By joining the semi-circular sections together as needed for a given load, and size column could be formed.

In the Calhoun Street Bridge the columns utilize four semi-circular sections, seven spans of 180' were used to cross the river.

The Phoenix Column bridges were among the last constructions of wrought iron, long the prime variety of iron used where great tensile strength and resistance to stress was required. By the 1880's open hearth steel had come to replace wrought iron for most of these uses, and bridges from that time were constructed primarily of steel girders.

In the 1885 Album of Designs of the Phoenix Bridge Company, the following description was given:

This roadway bridge was built for the Trenton Bridge Company of Trenton, NJ and crosses the Delaware River at that place [connecting on the Pennsylvania side with the Borough of Morrisville. There are seven spans with a total length of 1,280 feet. Each span contains nine panels of 20 feet each, and the depth of truss is 26 feet. There is a clear width of 20 feet for the roadway, and 6 feet for each of the two sidewalks.

"The design of this structure represents the most advanced system of construction as applied to the ordinary roadway bridge. Two lines of iron stringers extend the entire length of the seven spans, and carry at the center of each panel an intermediate transverse beam on which rests iron joists of half a panel length. All the economic and other advantages of long panels were thus made available besides eliminating everything combustible, with the unavoidable exception of the floor-plank and three lines of light-timber stringers to which they are spiked.

"The sidewalk railing serves the double purpose of a guard and trussed stringer for a portion of the sidewalk load. With its lines plainly expressive of the purpose of its construction, it materially contributes to the light and graceful, yet most substantial, appearance of the entire structure."

The significance of the Calhoun Street Bridge is that it is one of the few surviving long bridges of its type. While it is shorter and slightly less impressive than the Walnut Street Bridge in Harrisburg, PA, which it predates by six years. It is probably the longest Phoenix Bridge and is still open to traffic. It is also the second oldest bridge on the Delaware River preceded by Roebling's Lackawaxen Aqueduct.

The bridge is well-appreciated by local residents for its beauty and historic significance.

1. Packard, Vance, PA Historical and Museum Commission, Calhoun Street Bridge and/or Trenton City Bridge, nomination document, 1975, National Park Service, National Register of Historic Places, Washington, D.C.