BNSF Mississippi River Bridge (Nicollet Island)

Located on the west side of Nicollet Island, this large bridge carries a former Great Northern Railway mainline across the main channel of the Mississippi River. This crossing is among the oldest in Minneapolis, and has a long history. The first bridge at this location consisted of a wooden truss bridge, set onto timber substructures, which was completed in 1867. It is believed that this bridge was renewed with a similar bridge in the late 1870s or early 1880s. During the 1880s, other railroads in Minneapolis were constructing iron and stone bridges across the Mississippi River, providing a more durable structure. In 1891, contracts were awarded for replacing the main channel and east channel bridges at Nicollet Island with new double track iron and stone structures. Work on the main channel bridge was completed in mid-1892. This bridge consisted of two 173-foot, pin-connected Pratt through truss spans, approached by a 70-foot deck plate girder span on the east end and an 82-foot and a 57-foot deck plate girder span on the west end. By the mid-1920s, the bridge had become too light for traffic, and it was decided to reconstruct the crossing. Since there was no river navigation north of St. Anthony Falls, it was decided to replace the bridge with a deck plate girder bridge and shorten the structure. The new bridge would consist of one 82-foot, two sets of alternating 73-foot and 100-foot deck plate girder spans and a 35-foot deck plate girder span on the east end. In addition, a 96-foot and a 73-foot deck plate girder span would be provided for a curved spur to the Minneapolis Union Depot at the west end of the bridge. New concrete substructures would be constructed for the bridge, which would also reuse two stone piers. The 1892-era 82-foot spans were combined into a single double strength span and reused on the new bridge, and it is unclear if the trusses or other girders were also reused elsewhere. In the late 1950s, the City of Minneapolis began planning to develop the Upper Harbor, a project which would extend a navigation channel to North Minneapolis. In 1962, contracts were awarded for the alteration of the bridge, and in 1963, a through truss span was installed to replace the eastern 73-foot and 100-foot deck plate girders. Another major alteration occurred in 1987, when two additional beam spans were installed at the west end of the bridge to cross Great River Road and the 96-foot span serving the spur to the Union Depot was removed. The most recent alteration occurred in 2008, when the east approach was replaced as part of the now-defunct Northstar Commuter Line project, giving the bridge its present configuration.

Currently, the bridge consists of a 35-foot concrete modular girder span at the east end (span #1), a 171-foot, 7-panel, riveted Baltimore through truss span (span #2), a 100-foot (span #3), a 73-foot (span #4) and an 82-foot (span #5) deck plate girder spans and two 44-foot steel stringer spans (spans #6 and #7) at the west end. The bridge is set mainly onto concrete substructures, although portions of piers #4 and #5 are constructed of stone from the 1892-era bridge. The south track of span #5 uses four girder lines, which were originally fabricated for the 1892 bridge, while the remaining deck plate girder spans were fabricated in 1926. Several contractors were involved in constructing the bridge at several different times. Local contractors Ring & Tobin constructed the stone for piers #4 and #5, while the Edge Moor Bridge Works fabricated the south track girders for span #5. It is unclear if this span was altered by railroad company forces or by an unknown contractor. American Bridge Company fabricated spans #3, #4 and the north track of span #5. A. Guthrie & Company constructed the east abutment, piers #1, #2 and #3 and the alterations to piers #4 and #5. An unknown contractor fabricated the truss span, while St. Anthony Constructors constructed the alterations to piers #1 and #2 in 1963. This firm was a joint venture between Al Johnson Construction Company of Minneapolis and Peter Keiwit of Omaha, Nebraska; which had contracts for the construction of the Upper Harbor project. An unknown contractor fabricated the west approach spans, while an additional unknown contractor constructed the west pier (pier #6) and west abutment.

The truss span follows a design typical for mid-20th Century railroad truss spans, with heavy punch-plate members and a standard floor system. The top chord and endposts both used a built-up design, with a solid plate on the exterior and a punch-plate design on the interior. The bottom chord uses a similar design, with a square beam and a punch-plate design on both the top and bottom. All vertical members of the truss use heavy solid beams, while the diagonal members use a punch-plate beam design. The portal bracing consists of a heavy M-frame design, which is composed of punch-plate beams. The sway bracing uses a similar design, with the struts using a punch-plate design and the remaining bracing consisting of solid bars. The floor system consists of two stringers per track, which are connected to plate girder floorbeams at the panel points. Both the upper lateral bracing and lower lateral bracing consist of heavy steel bars. A majority of the deck plate girder spans use a standard design, with two heavy plate girders per span and a concrete ballast deck. The south track of span #5 uses four heavy iron plate girders and a concrete deck. The west approach spans use six shallow beams per track, and are covered by a concrete deck. Originally, the east approach consisted of a modified version of a standard deck plate girder span, with two plate girders and an angled bracing at each corner. This angled bracing may indicate that these spans were modified or reused from another location. The present east approach uses a standard modern design, with hollow precast concrete girders. The piers do not follow a standard design, but instead are the product of several modifications. In general, each pier has an angled nose and is a rectangular shape. Stone for piers #4 and #5 consists of Kettle River sandstone, quarried at Sandstone, Minnesota. The west approach pier uses a modern design, with three large round concrete pilings and a concrete cap. The east abutment uses a standard U-shaped design, while the west abutment is integral with a retaining wall.

Baltimore trusses became popular in the early 20th Century as an alternative to more traditional single intersection designs. These designs could be constructed heavier and spanned longer lengths. Mid-20th century versions of these spans were typically constructed using a punch-plate design, which superseded earlier laced member designs. Deck plate girder spans were popular for railroad use, as they were durable and easy to construct. Twinned girder spans were popular with railroads, as they allowed for a stronger span without requiring significant amounts of new material. However, it is somewhat unusual for these types of spans to be located on mainlines. Since the 2008 alterations, the bridge has seen no significant changes. Today, both tracks remain in regular use. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted in the structure. The author has rated the bridge as being moderately significant, due to the truss design and unique history.