| Name | UP Pigeon Creek Bridge (Crescent) Chicago & North Western Railway Bridge #1012 |
| Built By | Chicago & North Western Railway |
| Currently Owned By | Union Pacific Railroad |
| Superstructure Contractor | American Bridge Company of New York |
| Substructure Contractor | Unknown |
| Length | 143 Feet Total |
| Width | 2 Tracks, 1 In Use |
| Height Above Ground | 10 Feet (Estimated) |
| Superstructure Design | Subdivided Warren Through Truss |
| Substructure Design | Concrete |
| Date Built | 1937 |
| Traffic Count | 25 Trains/Day (Estimated) |
| Current Status | In Use |
| Chicago & North Western Railway Bridge Number | 1012 |
| Union Pacific Railroad Bridge Number | 343.35 |
| Significance | Moderate Significance |
| Documentation Date | 10/16/2015 |
In 1867, the Cedar Rapids & Missouri River Railroad (CR&MR) continued constructing a mainline westward from Boone, Iowa. In the late 1850s and early 1860s, the CR&MR had participated in constructing a line from Clinton, Iowa to Boone. The CR&MR was leased by the Chicago & North Western Railway (C&NW), which was seeking a route connecting Chicago to the Missouri River. In 1867, an impressive 150 miles were constructed between Boone, Iowa and Council Bluffs, Iowa, completing a connection between Chicago and the Missouri River. The line also allowed for a short spur from Missouri Valley, Iowa to the Missouri River opposite of Blair, Nebraska. This spur would eventually be extended across the Missouri River and into Nebraska. Between 1869 and 1872, Union Pacific Railroad (UP) constructed a bridge across the Missouri River between Council Bluffs and Omaha, Nebraska; and the C&NW obtained trackage rights over the bridge to reach Omaha. During the second half of the 19th Century, the C&NW had constructed and acquired a large amount of trackage throughout the Midwest. In 1884, the CR&MR was formally purchased by the C&NW; and this line quickly became a core asset of the C&NW system.
By the late 19th Century, traffic over this line had increased to the point significant upgrades were required. In 1893, a 5-mile section of railroad was relocated west of Jefferson, Iowa to improve grades and eliminate curves. One of the most significant barriers to efficient operation over this line was the Des Moines River Valley between Boone and Ogden, Iowa. The original route crossed the Des Moines River at Moingona, which was approached by winding and steep approaches on each bank. In 1899, C&NW subsidiary Boone County Railway (BCR) began construction on a more direct route between Boone and Ogden, Iowa; including a massive viaduct across the Des Moines River. The BCR was consolidated into the C&NW in 1900, and the new cutoff was completed in May 1901. The new alignment shortened the route by 3 miles, cut grades in half and only required two small curves. The original mainline through Moingona was maintained as an emergency backup and to serve industries in the area. Between 1901 and 1902, a second track was also constructed between Ogden and Council Bluffs, including a 5-mile realignment near Arcadia, Iowa. The double tracking of this line provided the C&NW with a well constructed double track mainline between Chicago and Council Bluffs.
By the 20th Century, the C&NW was operating an extensive railroad network, which radiated north and west from Chicago. The original mainline into Moingona was abandoned in 1930. This line served as the backbone of the C&NW, connecting transcontinental freight and passengers at Omaha to Chicago. Known as the Overland Route, this line became one of the most significant railroad routes in the United States. This route saw continuous upgrades during the 20th Century, including significant bridge, rail, tie and signal upgrades. In 1995, the C&NW was purchased by UP, which provided UP with a mainline into the railroad hub of Chicago. Into the 21st Century, the line has seen continuous upgrades, and remains one of the most significant railroad lines in the United States. Today, UP operates this line as the Boone Subdivision between Boone and Missouri Valley; and the Omaha Subdivision between Missouri Valley and Council Bluffs.
Located near Old Mormon Bridge Road west of Crescent, this large through truss bridge carries a former Chicago & North Western Railway mainline over Pigeon Creek. The first bridge at this location likely was a timber pile trestle, constructed when the line was first built. Between 1898 and 1902, the C&NW undertook a large double tracking project between Cedar Rapids, Iowa and Council Bluffs, Iowa. In 1902, a new double track through plate girder bridge was constructed at this location. In the mid-1930s, it was decided to straighten and channelize Pigeon Creek to mitigate flooding concerns. As part of the work, a larger bridge would be required. Construction on the new bridge began in late 1936, and was completed in early 1937. It is unclear if the previous bridge was reused at another location. Currently, the bridge consists of a double track 143-foot, 6-panel, riveted subdivided Warren through truss bridge, set onto concrete abutments. American Bridge Company fabricated the superstructure, while an unknown contractor constructed the abutments.
The truss span follows a typical design for the era, with heavily constructed members, a utilitarian portal bracing and a standard floor system. The top chord consists of a heavily built-up beam, composed of two channels connected by X-lacing on both sides. The endposts use a similar design, with two channels connected by X-lacing and thin transverse plates on both sides. The bottom chord is also heavily constructed, consisting of a solid box beam formed from two channels riveted together. All of the vertical members and diagonal members consist of massive solid beams, which are riveted to the top and bottom chords using large plates of different shapes and sizes. The floor system consists of large plate girder floorbeams at the panel points and two I-beam stringers per track. Unique to this bridge, the portal braicng uses a modified Warren design, which is connected by two struts and formed out of X-laced beams. The sway bracing and upper lateral bracing also consist of X-laced beams, and an additional transverse X-laced beam runs along the top bracing near the center of the truss. The abutments use a standard design, with short sloped wing walls. It is unclear if the entire abutment is concrete or if they are supported by concrete piles, a typical construction type from this era.
Warren trusses became popular around the turn of the 20th Century, as they are rigid and durable, while maintaining economy and a simple design. The C&NW had primarily used lattice truss designs between the mid-1870s and the 1920s, before switching to more traditional single intersection designs around 1930. Subdivided Warren trusses became popular in the 1920s and 1930s, and allowed for longer and stronger spans of a simple design. Since the initial construction, the bridge has seen no significant alterations. Today, only the west track remains in use as part of a heavily used Union Pacific Railroad mainline. Overall, the bridge appears to be in fair condition, with some defects noted throughout the structure. In particular, portions of the bridge appear to be exhibiting extensive pitting, possibly due to poor steel composition (see photos #10 and #11 above). The author has ranked the bridge as being moderately significant, due to the truss design and newer age.
Citations
| Build date and builder (superstructure) | American Bridge Company plaque |
| Railroad History Citation | ICC Valuation Information, Compiled by Richard S. Steele |