Wrought-Iron

The structure has two segments: an East Channel bridge consisting of four 175-foot spans and three 240-foot spans crossing from Harrisburg to City Island; and a West Channel bridge, consisting of seven 175-foot spans crossing from City Island to Wormleysburg.

With 15 truss spans totaling 2,820 feet, the Walnut Street Bridge is the finest and largest surviving example of the standardized Phoenix wrought-iron truss bridges produced from 1884 to 1923.

Built between 1819 and 1826, the Menai Bridge was the major structure on Britain's strategically important Holyhead Road connecting London with Holyhead and by sea to Ireland. Designed by Thomas Telford, the bridge's main span was 579 feet from tower to tower, the longest that had ever been attempted at this time. He used four sets wrought-iron eyebars to suspend the deck. These were made by William Hazledine at his Upton forge near Shrewsbury. Each bar was carefully tested in his Coleham shops before being pinned together and lifted into place.

The Second Street Bridge is a simply ornamented, wrought-iron structure. It is 18 feet wide and spans 225 feet over the Kalamazoo River. It was built to replace a dilapidated wooden bridge that had served the area for nearly 50 years.

The bridge is anchored to fieldstone abutments on each shore, and the deck is composed of wood beams. Iron lattice work provides structural stability and iron finials on the end posts provide aesthetic appeal. It includes a wooden pedestrian walkway.

The workforce consisted of less than 100 men, yet they finished construction in just 94 days. Such speed was possible due to the elimination of scaffolding. Instead, iron rods were used to support construction of the trusses between the towers, and workers moved back and forth across the rods. A dangerous venture, yet no workers were seriously injured.