Union Bridge Trail - Little Sioux River Bridge

Authors Note: This page has been written to reflect the configuration of this bridge at the time of abandonment.

Located south of Correctionville, this historic through truss bridge is the fifth crossing of a former Illinois Central Railroad branch line over the Little Sioux River. When the railroad was first constructed at this location, the bridge consisted of a single through truss span, set onto timber pile piers and approached by timber pile trestle spans on either end. Many railroads commonly used this technique when first constructing new lines, as it allowed for approach embankments to settle without damaging expensive components of bridges. In 1896, two new stone piers were constructed for the bridge, retaining the approach trestles. The bridge was again upgraded in 1911, when a portion of the south approach was replaced with a secondhand through truss span, and the approaches renewed. In 1958, the approaches were again renewed, giving the bridge its final configuration prior to abandonment. At abandonment, the bridge consisted of a 150-foot, 8-panel, Pratt through truss north span and a 123-foot, 8-panel, Pratt through truss south span. Both trusses are believed to have been constructed of wrought iron. The truss spans were approached by timber pile trestle spans on either end. The north truss span was supported by stone piers, while the south pier and approach bents were constructed of timber piles. The stone piers used a standard rectangular design with angled upstream noses. Stone for the piers was quarried at an unknown location, and the piers were constructed by an unknown contractor.

The northern truss was fabricated in 1887 by the Union Bridge Company at their Buffalo, New York plant. In the mid to late 1880s, the IC ordered a large quantity of truss spans from the Union Bridge Company for use on new branch lines and to replace existing light iron trusses. The northern span followed a standard design seen along this line, and was virtually identical to the third crossing of the Little Sioux River a few miles north of Correctionville. This span utilized built-up vertical members, a traditionally constructed floor and a decorative portal bracing. The top chord and endposts were composed of built-up beams, with a solid plate on the exterior and X-lacing on the interior. The bottom chord was composed of eyebars, with two sets of two at the center panels and two sets of one at the outer panels. Vertical members consisted of built-up beams, composed of tight X-lacing. The diagonal members consisted of eyebars and used a rectangular shape. Similar to other truss spans from this era, the outermost lower connections used a double connection design, with a pinned connection located above and below the floorbeam. The floor was composed of two plate girder stringers, which were affixed to plate girder floorbeams. Additional bracing was present between the two stringers. The lower lateral bracing was composed of metal rods, which were looped at the end and pinned into the floorbeams. The upper lateral bracing consisted of metal rods, and was affixed to the top chord. The portal bracing consisted of a crested lattice beam with rounded lattice heel bracing. The sway bracing was composed of solid beams, which were connected to the vertical members by a rounded lattice heel bracing.

The southern truss was fabricated in 1881 by the Keystone Bridge Company for use at the Tallahatchie River Bridge north of Abbeville, Mississippi. When that bridge was replaced in 1908, the three truss spans were released for reuse on this line. One span was installed at this location, while the other two spans were installed at thefourth crossing of the Little Sioux River, on the north side of Correctionville. This span was considerably lighter than the north span, with light built-up members, a light floor and less substantial portal bracing. The top chord and endposts were composed of built-up beams, with a solid plate on the exterior and light V-lacing on the interior. The bottom chord was composed of eyebars, with two sets of two at the center panels and two sets of one at the outer panels. These eyebars were spaced so each set is on an opposite side of the vertical member. Vertical members consisted of built-up beams, composed of a light V-lacing. The hip vertical members used a set of two light eyebars. The diagonal members consisted of eyebars and used a combination of a rectangular shape and slender rods. The floor was composed of four shallow steel stringers, arranged into two sets of two. These stringers were set on top of shallow floorbeams. It is unclear if this was the original configuration of the floor, as the floorbeams each had two slots formed by L-bars. The lower lateral bracing was composed of rectangular eyebars, which was pinned to a clevis in the floorbeams. The upper lateral bracing consisted of metal rods, which were threaded on each end, slid through a plate at the end of the sway or portal bracing and used an iron nut to be held in place. Both the portal bracing and sway bracing used a thin iron beam with no decorative features. The portal bracing also used a rounded T-shaped bar and decorative iron semicircle for heel bracing.

The Pratt truss design was the most popular railroad truss bridge design in the late 19th Century, as it was economical, durable and simple. However, the main limitation of this design was the length. In the mid-1880s, railroad spans of this design were generally limited to 200 feet or less, with most spans 150 feet or less. The northern span represented a typical sized span, and several similar examples were constructed for the IC. The southern span represented a typical iron truss span from the early 1880s. After abandonment, the bridge was originally left intact. It is unclear if the bridge was sold to Woodbury County at that time, or if it was sold to a private individual. In approximately 1995, the northern span and timber approaches were removed by a farmer, leaving only the southern span standing. Unfortunately, this greatly reduced the significance of the bridge. Recognizing the significance of the remaining span, Woodbury County rebuilt the bridge for pedestrian use in 2006. As part of the 2006 reconstruction, a concrete girder span was installed in place of the north span, and the approaches were replaced with modern steel stringer spans. The stone piers were rebuilt with concrete caps, and the approach spans rebuilt with steel pile bents. The bridge is now part of the Union Bridge Trail, despite the remaining span having no connection to Union Bridge Company. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked this bridge as being highly significant, due to the age, history and truss design. The remaining truss is among the oldest surviving truss bridges in the State of Iowa.