Grassy Point Swing Bridge

Located south of US Highway 2, this large through truss swing bridge crosses the St. Louis River. The first bridge at this location consisted of a single track 303-foot, pin-connected iron Pratt through truss swing span, set onto stone piers and approached by a lengthy trestle on each end. By 1912, the bridge had become too light and too narrow, and the bridge would be replaced. During the replacement of the bridge, temporary timber trestle shoefly was constructed to maintain traffic at this location. It is unknown if the old span was scrapped or reused elsewhere. Currently, the bridge consists of a double track 425-foot swing span, consisting of two 6-panel riveted Baltimore through trusses joined over a center pier by a tower. The swing span is approached by a through plate girder span on each end, and the through girder spans are approached by 18 spans of timber pile trestle on the west end and 63 spans on the east end. The bridge is set onto a combination of concrete and timber substructures. A significant portion of the approach trestles was filled with material dredged from the channel. In addition, the bridge was raised slightly. American Bridge Company fabricated the superstructure, while the Pittsburgh Construction Company constructed the piers and erected the span.

The swing span is composed of two 175-foot clear channels, and the two halves of the bridge are joined over a center swing pier by a large tower. The tower is connected to each half by heavily constructed eyebars, which meet at the upper angle connection. The swing span is a rim bearing design, where the structure is set onto a steel drum, which rotates on a roller nest. The truss span is heavily constructed, using tightly laced members, heavy riveted connections and a traditionally composed floor. The span uses a double X-frame portal bracing, with similar sway bracings. In addition to the riveted connections, the middle connection and interior upper angle connections use pin connections. The endpost and upper and lower chords of the span use heavily built-up beams. Each through girder span is also heavily constructed, using a traditionally composed floor, heavy girders and tapered and rounded girder ends.

Swing spans were commonly used where river navigation was required, and a vertical lift span would not be feasible. These bridges often used unique trusses to form halves of the swing span, and were often joined by a tower over a round swing pier. Northern Pacific bridge records indicate that the approaches were upgraded in 1960, although they have likely been upgraded since. The former eastbound (south) track has since been removed, and the trestle approaches have been reconstructed constructed for a single track. Currently, the bridge remains the only railroad crossing directly between Duluth and Superior. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked this bridge as being regionally significant, due to the movable truss design.