Wisconsin Dells Railroad Bridge

Located in Wisconsin Dells, this iconic deck truss bridge carries the former Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road) mainline over the Wisconsin River and Broadway (Wisconsin Highway 13/23). In the mid-1850s, the La Crosse & Milwaukee Railroad was constructing a line extending from Milwaukee to the Mississippi River at La Crosse, Wisconsin. Originally, the railroad planned to cross the Wisconsin River further south, near a town known as Newport. However, the railroad revised plans in 1856, and instead chose a more northerly route, opting to cross the river at a location with high limestone cliffs. In response, a new town known as Kilbourn City was platted near the east bank of the Wisconsin River, and contracts were let for the construction of the bridge in 1856. Prominent Chicago bridge builders Stone, Boomer & Boughton were awarded the contract to construct a wooden bridge, set onto stone piers. Work on the bridge began in late 1856, and the first train crossed the new bridge in December 1857. M. Alexander, a stonemason from Vermont was the foreman in charge of constructing the bridge, and Addison Smith was the carpenter in charge of the construction. Timber for the bridge was furnished by local contractors J. Bailey and Vanderopoel, Thayer & Company. The original superstructure was constructed almost exclusively of timber, and was designed using a Howe deck truss design. The first bridge consisted of a 56-foot span on the east end, a 247-foot span over the river, a 91-foot span over the river, and a 56-foot span over the west bank. The single track bridge was constructed at a width of 36 feet, and used three truss lines. The two main truss spans were covered by a tin covering. A stone pier was constructed in the river, and additional piers were carved into the limestone cliffs on either bank. Tall stone abutments were constructed at either end of the structure, and the substructures were constructed using stone quarried at an unknown location. In addition, a roadway was installed inside of the deck trusses, allowing for wagons and pedestrians to cross the river. The first structure cost approximately $100,000 to build; a tremendous cost for the time. A fire in May 1866 destroyed the first bridge, and a second bridge was constructed by Boomer & Company, reusing the stone piers and consisting of a similar design.

As traffic over this bridge increased, the wooden structure was no longer feasible to maintain. In addition, the wooden structure deteriorated quicker than anticipated. In 1877, the railroad awarded a contract to the Baltimore Bridge Company for a new iron bridge, and the iron was fabricated by the Edge Moor Iron Works. The new bridge was designed by prominent engineer C. Shaler Smith, who was the President and Chief Engineer of the Baltimore Bridge Company at the time. It is believed that the lengths of the spans were slightly altered when the new iron bridge was constructed, likely to help construct the new bridge without interfering with the old structure. As part of the work, the 1877 bridge reused the original 1857 abutments and center pier, and the limestone bluffs were modified for the new structure. The new bridge would be completed in early 1878, and would also include the lower roadway deck feature, similar previous structures. The new bridge consisted of a 56-foot, 4-panel, pin-connected deck truss span, a 243-foot, 13-panel pin-connected Whipple deck truss span and a pair of 69-foot, 4-panel, pin-connected Pratt deck truss spans at the west end of the structure. This bridge was entirely constructed of wrought iron, typical for bridges in this era. The roadway deck was located on the bottom of the main span, and was connected to the eastern 69-foot span by use of iron rod hangers. The 1877 bridge used modestly constructed members, consisting mainly of rolled beams and solid bars. In addition, an arched lattice endpost was located at either end of the main deck truss span. Similar to the previous structures, this bridge was also constructed for a single track. Whipple trusses were popular in the mid-19th Century, as they allowed for longer spans without requiring large amounts of additional material or complex designs. The Pratt truss approaches were lightly constructed, with the outer panels using a diagonal design instead of a typical rectangular shape.

By the early 20th Century, the iron bridge became outdated and too light for modern traffic. In addition, the Milwaukee Road was working to double track the line between Milwaukee and La Crosse. In 1902, the railroad began planning a new steel structure to replace the aging iron bridge. Work was started on the foundations of the new bridge in September 1902, with substructure work continuing into 1903. As part of the work, the two piers on the bluffs were modified to accommodate the new truss spans, and a new center pier would be constructed near the middle of the river. This center pier was comprised of stone laid to bedrock, topped with concrete. In addition, concrete additions were made to the abutments to account for the different depths of the spans. To erect the new spans, the new bridge was constructed around the old structure, with the old structure remaining in use until it was complete. The new bridge was completed in the middle of 1903. Reportedly, portions of the old structure were reused; while the remainder was scrapped. The new bridge consisted of two 166-foot Pratt deck truss spans, approached by a 54-foot deck plate girder span on the east end and a 51-foot deck plate girder span on the west end. Similar to previous bridges, a roadway deck was added underneath the main spans of the bridge. The only major alteration to the bridge came in 1955, when a new roadway bridge was constructed immediately south of this structure, removing the roadway deck from this bridge. As part of the project, the original 54-foot approach span was replaced by a new deck plate girder span, giving the structure its present configuration.

Currently, the bridge consists of a pair of 166-foot, 6-panel, pin-connected Pratt deck truss spans, approached by a 51-foot deck plate girder span on the west end and a 90-foot deck plate girder span on the east end. The west abutment is constructed of stone, and has been reused from the original 1857 structure. The two shore piers and center pier are both constructed of concrete, and the east abutment consists of concrete constructed in 1955. Phoenix Bridge Company fabricated the main spans, west approach and original east approach; while an unknown contractor fabricated the east approach. The 1903 concrete substructures were constructed by the Milwaukee Road Bridge & Building Department; while the east abutment was constructed by H.H. Mass Construction Company. The two main spans are heavily constructed, with large built-up members and a heavily constructed floor. The endposts and top chord are constructed of heavily built-up members, which are comprised of X-laced beams. The bottom chord is constructed of eyebars, typical for pin-connected bridges from this era. The diagonal members are also constructed of steel eyebars, and outer vertical members are constructed of rolled beams. Because the bridge was originally constructed for both a railroad and roadway deck, the main trusses use an unusual design with two floor systems, with the bottom system used instead of a lower lateral bracing. The upper floor consists of plate girder floorbeams and stringers, with two stringers per track. The bottom floor consists of a similar design, with plate girder floorbeams and two stringers placed near the bottom chord of the truss. Decorative heel bracing has been installed at the endposts of the truss, similar to the decorative features of previous bridges. The west approach uses a standard design, with heavy plate girders constructed with an open deck. The east approach uses a design that was common in the mid-20th Century, consisting of a ballast deck and four girders per track. All substructures are constructed using a standard design, with the center pier using a rounded design founded on a wider stone base, that is now hidden under the water. The shore piers are constructed by carving into the bluffs and reinforcing with retaining walls, while each abutment uses a square design with wing walls.

Typical of Milwaukee Road bridges, the main spans and west approach were designed by the Milwaukee Road Bridge & Building Department, and were fabricated as part of a larger order with the Phoenix Bridge Company, which included several major truss spans constructed between 1901 and 1903. By the turn of the 20th Century, many railroads had switched to using riveted truss designs, as they were stronger and provided greater rigidity. However, the Milwaukee Road continued to use pin-connected designs into the 1910, preferring the simplicity and proven nature of the structures. The Pratt truss design was arguably the most common truss design during the second half of the 19th Century, as the design was strong, durable, simple and economical. Since the 1955 approach replacement, the bridge has seen only minor alterations. A helper bent has been added underneath the active track of the structure to help reinforce the bridge. Currently, only the south track is in use, while the north track retains a deck but no rails. Overall, the bridge appears to be in fair condition, with no significant deterioration noted. Due to the heavy use and age, it is likely that this bridge will require some sort of strengthening or replacement in the coming years. The author has ranked this bridge as being regionally significant, due to the significance of this bridge in developing the community, the historic nature of the structure and the design.