Estherville Railroad Bridge (North)

Located on the west side of Estherville, this deck truss bridge carries a former Chicago, Rock Island & Pacific Railroad (Rock Island) line over the West Fork Des Moines River. The first bridge at this location was a long and tall timber pile trestle, likely with a wooden truss main span. In the late 1880s, the BCR&N began making significant improvements to this line, replacing timber bridges with iron, steel and stone structures. In 1889, most of the trestle was replaced with an iron viaduct and deck truss main span, set onto stone piers and iron towers. As part of the work, a significant amount of the trestle was filled on either end, with a short segment retained at the west end. In 1894, the remaining trestle was filled, and a new stone abutment and deck girder span added. Further alterations were made in 1903, when the east approach spans adjacent to the deck truss span were replaced with a much larger span. The most recent alterations to the bridge came in 1907, when the original truss span was replaced with a heavier secondhand truss span, giving the bridge its present configuration. Currently, the bridge consists of a 124-foot, 8-panel, pin-connected Pratt deck truss span, constructed with three truss lines and set onto stone piers which have been altered with concrete. The east approach consists of a pair of 48-foot deck plate girder spans, originally fabricated in 1889 and a 100-foot deck plate girder span, constructed in 1903. The east approach is set onto a stone abutment, an iron bent and a stone pier with a steel bent. The west approach consists of five 32-foot deck plate girder spans, originally fabricated in 1889 and a 46-foot deck plate girder span, originally fabricated in 1894. The west approach is set onto two iron towers, an iron bent and a stone abutment.

The deck truss span was originally fabricated in approximately 1880 by an unknown contractor for use at an unknown location, before being rebuilt and reused here. One possible location the span was reused from is the Iowa River Bridge at Iowa City, Iowa, which used identical 150-foot truss spans with 10 panels each. There is strong evidence that the truss span used here was shortened, such as empty rivet holes and a cut top chord. The Iowa City bridge was replaced in 1901, but used identical features to the trusses used here. When the truss span was installed here, a third truss line was added and the floor system appears to have been reconstructed. The truss has several features of an early 1880s truss span, with light built-up members, eyebars for the bottom chord and a relatively light floor system. The top chord is composed of a built-up beam, with a wide-set V-lacing on both sides. The bottom chord is composed of eyebars at the center panels, while the outer panel on each end uses a built-up beam with extremely light V-lacing. The eyebars at the center use two sets of bars. Both the vertical members and endposts use an identical built-up design, with a wide-set V-lacing and riveted plates at the top and bottom. Typical of spans from the 1880s, the diagonal members consist of rectangular eyebars, arranged into two sets of two. The floor system appears to be heavily modified, with light plate girder stringers and light plate girder floorbeams. In addition, the center truss acts as an additional stringer, with the ties set directly onto the top chord. The upper lateral bracing is composed of looped square bars, which are pinned into the upper corners of the floorbeams. At the bottom of the trusses, I-shaped bars connect the three trusses at the panel points. These bars have a U-shaped plate affixed to each end, which is pinned into the lower connections. Unique to this bridge, the lower lateral bracing consists of square bars with turnbuckles with eyebars at each end. At the eyebars, the bar is bent at a sharp angle, and the bracing is pinned into the lower connections of the outer trusses. The interior bracing consists of eyebars, which are pinned to the outer trusses and the lower corners of the floorbeams. The truss members have stamps indicating they were fabricated at Trenton, New Jersey. This rolling mill produced bridge members, and this type of markings were most commonly used between the mid-1870s and approximately 1880.

The approach spans also use a number of unusual features that are unique to this bridge. The eastern girders (spans #1 and #2) were fabricated in 1889 by an unknown contractor. These spans use two modest-sized plate girders, with an open deck. Span #3 was fabricated in 1903 by an unknown contractor, and reportedly weighed 140 tons upon installed. This span is considerably heavier than spans #1 and #2, with two deep girders, heavier interior bracing and an open deck. Spans #5 through #9 were also fabricated in 1889 as the same unknown contractor as spans #1 and #2. These spans are slightly lighter than the eastern spans, but follow a similar design. The western span (span #10) was fabricated in 1894 by an unknown contractor, and uses a slightly different design than the other girders. The bottom of the eastern end is tapered to match span #9, while the remainder of the girder is straight. This span is slightly heavier than spans #1, #2 and #5 through #9, but uses a similar design of interior bracing. The substructures also use a number of different designs, which reflect the different build dates. The east abutment consists of a standard rectangular abutment, while the west abutment uses a similar design with tall bearing blocks. An iron bent supports spans #1 and #2 (pier #1) and spans #9 and #10 (pier #9). These iron bents are composed of built-up X-laced beams, set into an A-shape. The bottom and middle of these bents are connected by a V-laced beam, while the tip is connected by a solid plate. Transverse lateral bracing is composed of square bars, which are looped on the ends and pinned at the top, middle and bottom of each beam. Iron towers support the remainder of the west approach (piers #5 through #8), with spans #6 and #8 forming the tower spans. The bents of these towers are identical to piers #1 and #9, and are connected by a longitudinal V-laced beam on the bottom and square looped iron bars, which are pinned at the top of each bent and at the longitudinal beam. The iron towers and bents are supported by concrete and stone pedestals, with the concrete pedestals likely replacing the original stone blocks in the 20th Century. Span #3 is supported by a large steel bent at piers #2 and #3. These bents are formed by two heavy X-laced beams, connected by large solid beams at the top, bottom and in a transverse X-shape. Piers #2, #3 and #4 use a standard rectangular design, with an angled upstream nose. Piers #3 and #4 have been modified by removing a portion of stone on the downstream side and replacing it with concrete, likely to accommodate a wider truss span. It is unclear if the stone and concrete substructures were constructed by an unknown contractor or by railroad company forces.

The BCR&N and successor Rock Island often pieced large bridges together, replacing portions at a time. The western span was likely constructed at a different time to allow the original approach embankment to settle. Railroads often used this technique to avoid damaging stone and metal bridgework, which was much more expensive to install than timber. Railroads often reused steel and iron spans, as it provided a cost effective way to replace bridges without requiring large amounts of new material. Oftentimes, when one bridge became too light for traffic, it could feasibly be retrofitted and reused at a new location. Adding additional truss lines was a common way to strengthen bridges with material already in stock. The Pratt truss design was arguably the most popular railroad truss bridge design during the second half of the 19th Century, as it was durable, simple and economical. These types of spans were superseded by riveted Warren trusses around the turn of the 20th Century, which were stronger without requiring significantly more material. Since the 1907 reconstruction, the bridge appears to have seen no major alterations, and remains in use. Overall, the bridge appears to be in fair to good condition, with minimal deterioration noted to any specific portion of the bridge. The author has ranked this bridge as being highly significant, due to the age, size and design of the bridge. With a c. 1880 fabrication date, the trusses on this bridge are among the oldest trusses in use in Iowa. The approach spans are also notable, due to the age of the spans, lightweight design of the iron towers and bents and large size of span #3.