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| Name | CN IA-4 Bridge Illinois Central Railroad Bridge #W401.0 |
| Built By | Illinois Central Railroad |
| Currently Owned By | Canadian National Railway |
| Superstructure Contractor | Unknown |
| Substructure Contractor | F.O. Montgomery Company of Sac City, Iowa |
| Length | 36 Feet Total |
| Width | 1 Track |
| Height Above Ground | 14 Feet 1 Inch |
| Superstructure Design | Through Plate Girder |
| Substructure Design | Concrete |
| Date Built | 1937 |
| Traffic Count | 3 Trains/Day (Estimated) |
| Current Status | In Use |
| Illinois Central Railroad Bridge Number | W401.0 |
| Canadian National Railway Bridge Number | 401.0 |
| Significance | Local Significance |
| Documentation Date | 4/22/2018 |
In 1857, the Dubuque and Pacific Railroad (D&P) began construction of a new mainline across central Iowa, which sought to link to the existing Illinois Central Railroad (IC) at Dubuque, Iowa. In May 1857, the first 29 miles were completed between Dubuque and Dyersville, Iowa. In March 1860, the line was completed an additional 49 miles from Dyersville to Jesup, Iowa. In 1860, the D&P was sold to the Dubuque and Sioux City Railroad (D&SC). The D&SC completed an additional 22 miles to Cedar Falls, Iowa in 1861; followed by an additional 43 miles to Iowa Falls, Iowa in 1866. By 1867, the IC had garnered interest in this line, and leased the D&SC. The following year, a bridge across the Mississippi River at Dubuque was completed to link this line and the IC line towards Freeport, Illinois. In August 1869, the Iowa Falls and Sioux City Railroad (IF&SC) completed an additional 49 miles from Iowa Falls to Fort Dodge, Iowa. In October 1870, an additional 135 miles were completed west to the Missouri River at Sioux City, Iowa. The IF&SC was also affiliated with the D&SC and IC; and was fully merged into the D&SC in 1888.
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 principal mainline for the company, connecting Chicago to the Missouri River at Sioux City. 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 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 Dubuque Subdivision between Dubuque and Waterloo, Iowa; the Waterloo Subdivision between Waterloo and Fort Dodge, and the Cherokee Subdivision between Fort Dodge and Sioux City.
Located in Pomeroy, this through plate girder bridge carries a former Illinois Central Railroad line across Iowa Highway 4. Prior to the construction of this bridge, a grade crossing existed at this location. In the 1920s and 1930s, the Iowa Highway Commission worked to improve highways throughout the state. As part of several projects, grade separations were proposed at busy railroad crossings. One of the proposed projects was a new underpass on Iowa Highway 4 (then Primary Road #17) on the east edge of Pomeroy. Contracts for the project were awarded in September 1936, with construction occurring throughout 1937. Currently, the bridge consists of a 36-foot through plate girder span, set onto concrete abutments. The superstructure uses an unusual design, with two heavy girders, square girder ends and a concrete encased floor system. Closed floor systems were used to help protect motorists below from falling debris from the railroad tracks. Most often, this was accomplished with various ballast deck designs. It appears that the floor system of this bridge consists of several parallel I-beam floorbeams, which were wrapped with steel mesh and encased with concrete. While durable and safer than other designs, this design undoubtedly significantly increases the dead load on the span. The substructures follow a standard design, with sloped wing walls extending perpendicular from the bridge. An unknown contractor fabricated the superstructure, while F.O. Montgomery Company constructed the substructure. Through plate girder spans were popular with railroads, as they were durable and easy to construct. Since the initial construction, the bridge has seen no significant alterations, and remains in use. Overall, the bridge appears to be in good condition, with only minor surface rust to the girders and minor spalling to the floor and substructures. The author has ranked this bridge as being locally significant, due to the common design.
Citations
| Build date | Illinois Central Gulf Railroad Iowa Division 1973 Track Profile |
| Builder (substructure) | The Sioux City Journal; September 2, 1936 |
| Railroad History Citation | ICC Valuation Information, Compiled by Richard S. Steele |