Chaska Swing Bridge

Located between Chaska and Shakopee, this unique swing bridge once carried the Chicago, Milwaukee, St. Paul & Pacific Railroad over the Minnesota River. In the 19th Century, the Minnesota River was considered navigable to steamboat traffic as far upstream as New Ulm. However, upstream of Shakopee, the river was often not suitable for reliable commercial navigation, and the channel was filled with sand bars, snags and sharp bents. When railroads first constructed bridges across the Minnesota River, structures were required to be movable bridges, which allowed for commercial navigation. The first bridge at this location was constructed in 1871, and likely consisted of a wooden swing bridge, set onto timber substructures. In 1879, the bridge was reconstructed with a new timber truss bridge, with a 250-foot swing span and a 127-foot approach span, set onto new stone substructures. The abutments of the bridge consisted of lengthy stone parapet abutments, and a timber stringer span was set on top of the abutments. The superstructure may have been replaced again in the 1880s, likely retaining the timber truss design.

In 1900, the bridge would be upgraded by replacing the original swing span with a new steel through truss swing span. The approach span was replaced in 1905, using a span originally constructed across the Zumbro River at Kellogg, Minnesota in 1886. As part of this work, a concrete portion was added in front of the original stone abutment. This span quickly became unsuitable for this location, and would be replaced by a riveted through truss span, which had been constructed in 1905 for the bridge at Kellogg. The old span would be relocated to Eau Claire, Wisconsin. In 1918, a timber pile bent would be added in front of the east abutment, which had begun to fail. The stringers on the abutments were last replaced in 1943. The final configuration of the bridge included a 250-foot, pin-connected Pratt through truss swing span, consisting of two 6-panel leaves joined by a triangular tower over a center pivot pier. This span was approached by a 127-foot, 5-panel riveted Pratt through truss span on the west end. The main bridge would be approached by a 20-foot timber stringer span on the east abutment, and a 33-foot timber stringer span set on the west abutment.

The swing span used a standard Milwaukee Road design, which was constructed at a handful of locations in the late 1890s and very early 1900s. This span used heavily laced upper and lower chords, with a combination of built-up and solid bar members. The lower chord of the swing span was placed slightly above rail height, which allowed for a heavy floor to be constructed. This floor consisted of heavy plate girder stringers and floorbeams. The tower of the swing span consisted of two sets of built-up beams, which were connected to form an "A" shape. The tower was connected to the upper angle connection of the swing span by solid bars. In addition, the span had a lattice style portal, with solid heel bracing. The approach span used a typical Milwaukee Road design for the era, with heavily built-up members, a traditionally composed floor and lattice portal bracing with star cutouts on the heel bracing. Typical of Milwaukee Road spans, both spans were designed by the railroads Bridge & Building Department. The swing span was fabricated by an unknown contractor, while a missing plaque indicated that Wisconsin Bridge & Iron Company fabricated the approach span. It is currently unknown if the stonework was constructed by an unknown contractor or by railroad forces. The stone appeared to have been quarried nearby, and had a distinct yellow color.

Pratt through trusses were the most common railroad truss bridge design during the late 19th Century. These spans were durable, economic and simply designed. These spans were built exclusively with pinned connections in the 19th Century. As riveted connections spans became popular in the early 20th Century, many railroads switched to using a Warren design. However, the Milwaukee Road used in-house design, which led to the railroad using Pratt designs for far longer than some railroads. The evolution of only five years of truss bridge design was clearly on display at this structure. The swing span used a rim-bearing swing span design, where the span is set onto a steel drum, which rotates over a roller nest that runs on a track. A center gear allowed the swing span to rotate. Rim bearing swing spans became the standard swing span design by the turn of the 20th Century, as they required less precise engineering and were easier to maintain. Railroad records indicate that the swing span was operated by hand, and could be turned by a single operator. The ends of the swing span were set onto large rollers, placed on the pier and east abutment. These rollers were different from later rollers introduced by the Milwaukee Road, as they did not contain a lifting mechanism. It is unknown how many times the bridge actually opened, or when it last opened. Navigation upstream of Carver ceased prior to 1917. It appears that the span was still capable of turning well into the 20th Century, although permanent locks were likely installed to prevent the span from shifting.

Despite the branch line status, the structure remained well maintained into the second half of the 20th Century. The bridge remained unchanged until the 1980s, when it was converted to trail use as part of the Chaska-Shakopee Trail. The trail was one of the first rail-trails in Minnesota, and instantly became popular in the growing suburbs of Chaska and Shakopee. As part of the conversion to a trail, a wooden deck was added over the original railroad ties, and chain link fencing added for handrails. It is not believed that any further repairs were made to the bridge at that time. This bridge became an iconic part of the trail, and became a local landmark for the two communities. One newspaper article estimated that 2,000 people would cross the bridge on any given weekend day during the summer. In the summer of 1996, the center pier of the bridge was found to be rapidly sinking into the river, causing the bridge to lean significantly. It was determined that the rivers current caused a scour hole to open near the pier, causing the pier to sink.

Because of the rapidly sinking pier, it was decided that quickly removing the bridge was the only safe option. On August 22nd, 1996; the bridge was demolished with explosives. After the bridge was dropped to the river, the steel was cut up for scrap, and the piers and east abutment removed. The west abutment was left intact, likely to preserve the survey marker placed in the concrete. A significant amount of stone from the piers was placed at a parking lot near Minnesota Highway 41. With the bridge removed, there was no viable crossing of the Minnesota River, and the Chaska-Shakopee trail significantly declined in popularity. A new connection would not be created until 2008, when the Minnesota Highway 41 bridge was replaced. Despite the removal of the bridge, the author has ranked the bridge as being regionally significant. This ranking is due to the extensive history of the structure, swing span design and the lack of truss bridges in Carver County. As of 2025, the only remaining portion of the bridge is the west abutment, and much of the trail between the west abutment and Chaska has been severely damaged by flooding.