McKinley Bridge

View an article describing the construction of this bridge

View an article describing the construction of the superstructure

View an article describing the construction of the substructure

In the early 20th Century, the Illinois Traction System was a rapidly expanding interurban railroad, connecting major cities throughout central Illinois. The railroad was formed by William Brown McKinley, consolidating several smaller electric railroads in central Illinois. The IT had significant terminals across the Mississippi River from St. Louis, Missouri; but did not own a bridge across the Mississippi River to reach St. Louis. The St. Louis Electric Bridge Company was charted to construct a bridge across the Missouri River for the IT, connecting to terminals in St. Louis. During the planning stage of the bridge, the promoters of the company determined that a bridge serving railroad, wagon and pedestrian traffic would have the greatest benefit for the railroad company. The general requirements determined by the War Department specified a bridge with 500-foot channel spans at low water, and a 50-foot clearance at high water. Famed Polish-American engineer Ralph Modjeski was hired to design a new bridge meeting these requirements. A suitable site was found approximately 3/4 mile south of the Merchants Bridge. A bridge was designed using Pennsylvania through truss main spans, approached by deck truss spans and a steel girder viaduct.

In July 1909, the Missouri Valley Bridge & Iron Company was awarded the contract to construct nine piers for the bridge, and to erect the superstructure. The contract for the truss superstructure would be awarded to the Pennsylvania Steel Company. The contract for the superstructure and erection of the approaches was awarded to Strobel Steel Construction Company, and the approach substructures would be constructed by American Concrete Company. The four main piers of the bridge would be constructed using pneumatic caissons, set onto bedrock. These piers would be faced with limestone quarried at Bedford, Indiana. Below the low water line, the piers would be constructed with red granite. The remaining piers would be constructed of concrete. The approach spans would be set onto steel towers and bents, supported by concrete pedestals and abutments. Construction on the piers was began in late 1909, with the first caisson reaching bedrock in December of that year. After the completion of piers #1 and #2, erection began on the main truss spans, before being stopped due to high water in December 1909. On December 31st, 1909; high water washed away the falsework for the center span of the bridge. Construction was again delayed due to ice jams in January 1910, which damaged the construction site. Work on the substructures was completed in the spring of 1910. The bridge opened to traffic in November 1910. The bridge would be named the McKinley Bridge, after William B. McKinley. When completed, this bridge was the third bridge across the Mississippi River at St. Louis, and the second for non-railroad traffic. The main spans of the bridge carried two railroad tracks in the center of the bridge, with a roadway deck on either side of the tracks. These decks would be connected to the main trusses by use of brackets. The original approach viaducts for the roadway and railroad were separate structures, running parallel to each other.

The main section of the bridge utilized three 18-panel, pin-connected Pennsylvania through truss spans. The center span of the bridge would be 523 feet long, and set level. The two outer spans would utilize 521-foot spans, set at a 0.75% grade. The main spans of the bridge were constructed with built up members, 12-inch pins and an X-frame portal bracing. These trusses were heavily constructed, with a depth of 78 feet at the center of the trusses. The west side of the bridge would be approached by a 250-foot, 8-panel, pin-connected Warren deck truss span, and two 150-foot, 6-panel spans of the same design. The east side of the bridge would be approached by an identical 250-foot and 150-foot span. The deck truss spans were set at a 1.75% grade. The 250-foot spans of the bridge used a curved lower chord, a unique design occasionally seen in longer truss spans. The center of these trusses were 40-feet deep, and the inside ends of these trusses set into recesses in piers #1 and #4. The floor systems of all trusses would be constructed of plate girders. The original deck of these spans would consist of railroad ties, with bituminous blocks between the rails.

The original west approach of the bridge consisted of a 98-foot deck plate girder span over the Chicago, Burlington & Quincy Railroad, followed by twenty-six 41-foot deck plate girder spans, a 106-foot through plate girder span over Hall Street and the Terminal Railroad Association tracks, eighteen additional 41-foot deck plate girder spans, a through plate girder span over 2nd Street, seven more 71-foot deck plate girder spans, and a through plate girder span over Broadway. An additional viaduct on the north side of the bridge from Broadway to Hall Street carried an industrial track, which dropped to ground level to interchange with the CB&Q. This additional viaduct utilized the same design and lengths as the main viaduct. The east approach viaduct originally consisted of eighteen deck plate girder spans, with three 50-foot spans and the remainder ranging from 39 to 41 feet. A sharp curve was located near the end of the viaduct. A temporary wooden pile trestle approach served the railroad, with the intention that the trestle spans would be filled or replaced with steel spans. The deck of these approach viaducts consisted of two railroad tracks running down the middle, and road lanes running on the outside. The substructures of these spans included steel bents and towers, supported by concrete pedestals and concrete abutments. The outside of the tower spans utilized deck truss spans to support the roadway deck.

Later additions to the bridge would include additional railroad viaduct approaches on the east and the southwest legs of the McKinley Bridge. In 1927, the St. Louis, Troy & Eastern Railroad would construct a lengthy double track viaduct approach on the east leg of the bridge. Starting at the curve in the original viaduct, the new viaduct ran through Venice, crossing streets, railroads and residential areas. From the east end, this viaduct consisted of sixteen deck plate girder spans of varying sizes, a 60-foot deck plate girder span over Main Street, two 70-foot deck plate girder spans, two 110-foot and one 65-foot deck plate girder spans across the C&A/Wabash, and nineteen additional deck plate girder spans through a residential area of Venice, crossing 2nd, 3rd and 4th Streets. Several spans of single track wooden trestle were used across a flood plain, and two 60-foot deck plate girder spans crossed a leg of the Terminal Railroad Association wye. Additional trestle spans were used before two unique through truss spans and ten 60-foot deck plate girder spans crossed the TRRA yard in Brooklyn. The entire bridge was set onto concrete, steel bent and steel tower substructures. The timber trestle portion of the bridge would be set onto timber pile substructures. The through trusses at the east end of the viaduct were unique. The western span would be a 125-foot, 4-panel riveted Pratt through truss span, set at a heavy skew. The eastern span would utilize a unique riveted 5-panel Warren through truss design, with one truss web 160 feet long and the other 130-feet long, built to compensate for a heavy skew and curve. These trusses used particularly long panel lengths, and were built for two tracks. It is not believed a second track was ever installed on this portion of the viaduct. This viaduct provided a more direct connection to the McKinley Bridge for the Illinois Terminal Railroad, successor of the Illinois Traction System.

A second double track viaduct was constructed in 1931 by the McClintic-Marshall Construction Company, to connect to industrial areas and a new terminal south of this bridge. Known as the Branch Street Trestle, the viaduct left the main structure on the west side of the 250-foot deck truss span. The viaduct would utilize 16 spans of alternating 60-foot and 40-foot deck plate girders, set onto steel towers. Eighteen steel stringer spans would follow, with a 48-foot deck plate girder span over Angelrodt Street, fourteen more 20-foot steel stringer spans, two 30-foot steel stringer spans and eighteen steel stringer spans. The steel stringer spans would be set onto concrete towers and bents. The line would be continued south, eventually ending in a tunnel under Tucker Boulevard.

Pennsylvania through truss spans became popular with railroads during the late 1890s. This design offered a stronger and more economical alternative to the Whipple design, which had dominated long span construction through the 1870s and 1880s. The Whipple design offered several disadvantages, and railroads were eager to find a suitable span design for long spans. In the early 20th Century, most long railroad trusses utilized the Pennsylvania design, or some variant of this design. The Pennsylvania design is characterized by the subdivided truss web, a variant of the Pratt design, as well as a curved chord. Both the Merchants Bridge and the MacArthur Bridge nearby utilized similar designs. Spans of this length were considered feats of engineering, and were often admired by the engineers who designed them. There is significant evidence that Ralph Modjeski was extremely proud of this bridge, likely due to the extremely long length of the trusses. The approach deck trusses also utilized a unique design, using the Warren design with pinned connections. The Warren design superseded the Pratt design in the early 20th Century, but was most often used with riveted connections. Long viaducts of girder spans were often used in cases like this, as the design provided the most durable and economical design for bridges spanning long lengths. The entire bridge was built for class-one railroad standards and heavy locomotives, later carrying heavier diesel locomotives.

Beginning in the 1930s, Interurban Railroads declined throughout the United States, particularly due to automobile use. The Illinois Terminal was acquired by nine class-one railroads in 1956, which operated the trackage as a short line. Because significant portions of the route paralleled other, better built railroad lines, most of the IT would be abandoned. The City of Venice acquired the bridge in 1958, operating tolls to use the bridge. Railroad traffic across the McKinley Bridge ended in 1977, and the tracks were paved over. In 1994, the bridge underwent a limited rehabilitation, including removal of the railroad tracks. The bridge would enter a state of disrepair, and be closed to all traffic in 2001.

In 2004, the Illinois Department of Transportation (IDOT) gained control of the bridge from the City of Venice. IDOT funded a major reconstruction of the bridge and approach viaducts. The three main trusses would be retained, with the remainder of the structure demolished, with the exception of the Branch Street Trestle. Between 2004 and 2006, all of the viaducts in Illinois would be demolished, with the exception of a short segment near at east side of the Venice Trestle. New steel girder and concrete approaches would be constructed for the bridge to carry roadway traffic, with the former cantilevered roadway decks converted to pedestrian use. The rehabilitated bridge would open to traffic in 2007, and the Branch Street Trestle would be rehabilitated and opened for pedestrian use in 2008.

In 2024, the bridge continues to serve Cedar Street in Venice and McKinley Street in St. Louis. The demolition of the approach viaducts reduced the significance of this historic bridge. However, the biggest loss of historic significance to this bridge was the removal of the deck truss spans. It is believed that these spans were in too poor of condition to reuse in the rehabilitated bridge, and were likely not capable of carrying the modern loads required. Overall, the bridge appears to be in good condition, with the main trusses beautifully restored. It is hoped that the bridge will continue to carry traffic for many years to come. The author has ranked this bridge as being highly significant, due to the history, age and unique length of the truss spans.