MILW Wisconsin River Bridge (Merrill)

Located in Merrill, this through truss bridge carries the former Chicago, Milwaukee, St. Paul & Pacific Railroad New Wood Line across the Wisconsin River. At this location, a large island separates the two channels of the Wisconsin River. The first bridge across the west channel consisted of a timber pony truss bridge, originally constructed in 1895. This first bridge used a 68-foot and a 93-foot Howe pony truss spans, which were set onto timber pile piers and approached by timber pile trestle. The bridge was rebuilt in 1909, when the pony truss spans were replaced by a pair of 68-foot spans of the same design. By the late 1920s, the bridge again needed to be renewed. Instead of replacing the bridge with another wooden truss span, it was decided to reuse a steel truss span from another location, and rebuild the timber approaches and piers. In 1929, the present bridge was constructed, and the approaches were last renewed in 1959. Currently, the bridge consists of a 113-foot, 5-panel, pin-connected Pratt through truss span, approached by nine spans of timber pile trestle on the east end and four spans on the west end. The entire bridge is set onto timber pile substructures. The main truss span was originally fabricated in 1895 by the Lassig Bridge & Iron Works, and was likely part of a larger structure at an unknown location. Two identical spans at Spring Green, Wisconsin were installed in 1927; and a third identical span was installed at Jefferson, Iowa in 1930, likely indicating a connection between these spans. While the author cannot confirm where the spans may have come from, it is possible that they were originally constructed for Bridge #I-702 across the Grand River at Chillicothe, Missouri and shortened upon relocation.

The truss span uses a standard 1890s design for the Milwaukee Road. The top chord, bottom chord and endposts are comprised of built-up channels connected by X-lacing. A portion of the top chord has a splice plate, possibly indicating the span was shortened. The vertical members of the bridge are constructed of channels with a tight V-lacing. Typical for truss bridges from this era, the diagonal members are composed of slender bars. Portal bracing on the span uses a lattice design, with a rounded solid plate for heel bracing. The sway bracing uses a V-laced bar, with diagonal bars connecting to the vertical members. The upper lateral bracing is composed of thin rods, which are screwed into hooks, which are pinned to the tops of the sway and portal bracing. Pratt trusses were the most popular truss bridge design in the second half of the 19th Century, as they were strong, simple and economical. By the turn of the 20th Century, this design fell out of favor with innovations to riveted truss designs. Railroads often reused steel spans, as it was a cost effective way to upgrade bridges without requiring large amounts of new material. Often, when a span was no longer adequate for mainline use, it could feasibly be reused on a branch line with or without alterations. The bridge was last used in the 1970s to serve industries on the west side of the Wisconsin River, and has remained abandoned since. Despite being abandoned for over 50 years, the bridge appears to be in fair to good condition, with no major deterioration noted to the truss span. The bridge is in a good location to possibly be used for a pedestrian crossing, connecting the River Bend Trail on the east to neighborhoods west of the Wisconsin River. The author has ranked this bridge as being moderately significant, due to the truss design and unknown history.