WSOR Rock River Bridge (Janesville, North)

Located in Janesville, this large deck plate girder bridge carries a former joint line of the Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road) and the Chicago & North Western Railway (C&NW) across the Rock River. A bridge has existed at this location since the mid-1850s. The first bridge at this location likely consisted of a single track wooden deck truss bridge. In the mid-1860s, the bridge was again upgraded with a new double track wooden deck truss bridge. As traffic on this line increased in the 1870s and 1880s, a wooden structure was no longer acceptable at this location. In 1883, the wooden bridge would be replaced by a new double track iron deck truss bridge, set onto stone piers and approached by a stone arch span on either end. While railroad records indicate the stonework was constructed for this bridge, it is unclear if the stonework may be older. This bridge consisted of three 122-foot, 8-panel, pin-connected Whipple deck truss spans, composed of three truss lines per span. The superstructure was fabricated by the Keystone Bridge Company, and the superstructure was erected by the Baird Brothers. By the 20th Century, the deck truss bridge had become too light for traffic, and in 1913, the bridge would be replaced by the present structure. It is believed that the iron trusses were scrapped and were not reused elsewhere.

Currently, the bridge consists of four 63-foot and two 62-foot deck plate girder spans, approached by a 20-foot stone arch span on either end. The north pier (pier #1) and south pier (pier #7) were modified by adding a concrete portion to the top, while piers #3 and #5 were modified by encasing the stonework and adding a concrete portion to the top. Piers #2, #4 and #6 are constructed of concrete, and were built new for this bridge. It also appears that these piers were constructed wide enough for a potential third track. As part of the work, the top course of stonework was removed from the approaches, and new concrete deck panels were added to the tops. The superstructure uses a standard design, with two heavy plate girders per span, which are covered by standard precast concrete deck panels. The substructures also use a standard design, consisting of rectangular concrete piers. Milwaukee Bridge Company fabricated the spans for the west (Milwaukee Road) track, while American Bridge Company fabricated the east (C&NW) track spans. Cleary-White Construction Company constructed the concrete substructures, while the original stone approaches and substructures were constructed by an unknown contractor. Deck plate girder spans were commonly used by railroads, as they were durable and easy to construct. Since the initial construction, the bridge has seen few alterations, and only the east track remains in use. Overall, the bridge appears to be in fair condition, with no significant deterioration noted to the superstructure or substructures. However, the precast deck panels are extremely spalled and in very poor condition. Plans are underway to rehabilitate or replace this bridge, with work expected to begin in 2026 or 2027. The author has ranked this bridge as being moderately significant, due to the large size and stone arch approaches.