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| Name | CN Wall Lake Outlet Bridge Illinois Central Railroad Bridge #WA422.4 |
| Built By | Illinois Central Railroad |
| Currently Owned By | Canadian National Railway |
| Contractor | Unknown |
| Length | 42 Feet Total, 14 Foot Spans |
| Width | 1 Track (60 Feet) |
| Height Above Ground | 10 Feet (Estimated) |
| Superstructure Design | Concrete Arch |
| Substructure Design | Concrete |
| Date Built | 1911 |
| Traffic Count | 2 Trains/Day (Estimated) |
| Current Status | In Use |
| Illinois Central Railroad Bridge Number | WA422.4 |
| Canadian National Railway Bridge Number | 422.4 |
| Significance | Moderate Significance |
| Documentation Date | 12/30/2018 |
Between 1857 and 1870, the Dubuque and Sioux City Railroad (D&SC) had acquired and constructed a mainline across central Iowa, extending from the Mississippi River at Dubuque, Iowa to the Missouri River at Sioux City, Iowa. The D&SC had operated under lease from the Illinois Central Railroad (IC) since 1867, and connected to the IC system by using a bridge across the Mississippi River at Dubuque. This line provided several opportunities for the construction of branch lines. By the late 19th Century, the IC desired to enter the Council Bluffs, Iowa/Omaha, Nebraska markets. In 1890, the Omaha Bridge & Terminal Railway (OB&T) began construction on a line extending between Council Bluffs, Iowa and Omaha, Nebraska. A new bridge was constructed across the Missouri River between 1893 and 1894, with the goal of breaking the Union Pacific Railroad (UP) monopoly of traffic crossing the Missouri River at Omaha. Between September 1898 and January 1900, the Fort Dodge and Omaha Railroad (FD&O) constructed a 131-mile railroad line, extending from the existing D&SC mainline at Tara, Iowa to Council Bluffs, Iowa. The FD&O and OB&T were both leased by the D&SC/IC in 1899.
By the late 19th Century, the IC had developed and operated a sprawling railroad network in the central United States. This line served as a secondary mainline for the company, connecting Chicago to the Missouri River at Omaha. In the 20th Century, the IC had become a respected railroad, connecting several major cities in the central United States. The D&SC was fully merged into the IC in 1946. In 1972, the IC merged with the Gulf, Mobile & Ohio Railroad (GM&O) to form the Illinois Central Gulf (ICG). The bridge across the Missouri River was placed out of service in approximately 1980, although the tracks remain today. The entire IC system in Iowa, as well as the line between Dubuque and Chicago, were sold to the Chicago Central & Pacific Railroad (CC&P) in 1995. In 1988, the ICG was reorganized as the Illinois Central Railroad (IC). In 1996, the CC&P was repurchased by IC and in 1998, IC was purchased by the Canadian National Railway (CN). Today, CN operates the Omaha Subdivision between Tara and Council Bluffs.
Located near Carnarvon, this triple concrete arch bridge carries a former Illinois Central Railroad line over the Wall Lake Outlet. The first bridge at this location was likely a timber pile trestle, constructed when the line was first built. Several structures along this line were initially built as timber bridges, which allowed for approach embankments to settle without damaging more expensive permanent bridge work. Between the late 1900s and early 1930s, the approach embankments had satisfactorily settled, and the IC undertook a program to construct permanent bridges at waterway and roadway crossings. The present bridge at this location was constructed in 1911. Currently, the bridge consists of three 14-foot concrete arches, set onto concrete substructures and constructed at a width of 60 feet. The bridge follows a standard design, with semicircular arches, rectangular piers and stepped wing walls extending perpendicularly from the bridge. It is unclear if the bridge was constructed by railroad company forces or by an unknown contractor. Concrete arches were popular for railroad use, as they were durable and easy to construct. Since the initial construction, the bridge has seen no significant alterations, and remains in regular use. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked this bridge as being moderately significant, due to the common design and size. It is believed that this is among the only triple arch bridges in the State of Iowa.
Citations
| Build date | Illinois Central Railroad Valuation Engineering Field Notes at the National Archives |
| Railroad History Citation | ICC Valuation Information, Compiled by Richard S. Steele |