- 1867: 16 miles completed from Ackley to Eldora, Iowa by the Eldora Railroad and Coal Company
- 1868: 27 miles completed from Eldora to Marshalltown, Iowa by the Iowa River Railway
- 1868: Eldora Railroad and Coal Company sold to the Iowa River Railway
- 1869: Iowa River Railway sold to the Central Railroad Company of Iowa
- 1871: 65 miles completed from Northwood to Ackley, Iowa by the Central Railroad Company of Iowa
- 1871: 81 miles completed from Marshalltown to Albia, Iowa by the Central Railroad Company of Iowa
- 1878: Central Railroad Company of Iowa sold to Central Iowa Railway
- 1882: 98 miles completed from Oskaloosa to the Mississippi River across from Keithsburg, Illinois by the Chicago, Burlington & Pacific Railroad
- 1882: CB&P sold to the Central Iowa Railway
- 1883: 83 miles completed from Keithsburg to Peoria, Illinois by the Central Iowa Railway Company
- 1886: Mississippi River Bridge completed at Keithsburg by the Keithsburg Bridge Company
- 1889: Central Iowa Railway sold to the Iowa Central Railway
- 1895: Minneapolis & St. Louis Railway reorganizes as the Minneapolis & St. Louis Railroad
- 1901: Iowa Central Railway controlled by the Minneapolis & St. Louis Railroad
- 1901: Keithsburg Bridge Company sold to the Iowa Central Railway
- 1912: Iowa Central Railway sold to the Minneapolis & St. Louis Railroad
- Ca. 1920: Minneapolis & St. Louis Railroad reorganizes as the Minneapolis & St. Louis Railway
- 1960: Minneapolis & St. Louis purchased by the Chicago & North Western Railway
- 1962: Beacon, Iowa to Eddyville, Iowa segment abandoned, operations begin over parallel Rock Island tracks
- 1971: Oskaloosa, Iowa to Keithsburg, Illinois segment abandoned
- 1976: Keithsburg, Illinois to Middle Grove, Illinois segment abandoned
- 1988: Hampton, Iowa to Ackley, Iowa segment abandoned
- 1990: Rockwell, Iowa to Sheffield, Iowa segment abandoned
- 1995: C&NW purchased by Union Pacific Railroad
- 2001: Eddyville, Iowa to Albia, Iowa segment abandoned
- 2001: Sheffield, Iowa to Hampton, Iowa segment abandoned
- 2006: Ackley, Iowa to Marshalltown, Iowa segment sold to the Iowa River Railroad
- 2008: Middle Grove, Illinois to Peoria, Illinois segment abandoned
- 2011: Steamboat Rock, Iowa to Marshalltown, Iowa abandoned and purchased by Marshall and Hardin Counties
- 1995-Present: Union Pacific operates the Oskaloosa Subdivision between Marshalltown and Eddyville
- 2006-Present: Iowa River Railroad operates between Ackley and Steamboat Rock
- 2011-Present: Iowa River Rail Trail being developed between Steamboat Rock and Marshalltown
Located south of Marshalltown, this unique through truss bridge crosses Timber Creek.
Built in 1901 to replace a previous, lighter bridge; this bridge a single unique through truss span with riveted connections. Unlike some of the other trusses on this route, this bridge is a Pratt through truss, despite the fact that the tension and compression members both cross two panels. In addition, the endposts on this bridge cover two panels, making it a 6 panel structure.
Between Oskaloosa and Eddyville, numerous similar bridges were constructed. However, this bridge is different, as it features heavy rolled steel vertical members, and massive laced box girders for the diagonal members. It rests on stone abutments, encased in concrete.
Diagram of this style bridge
Unfortunately, no plaque can be found on the bridge. More research is being done on the bridge, to determine who designed and built the bridge.
Overall, the bridge appears to be in fair to good condition, with little serious deterioration. Some spalling has begun to occur on the abutments. In addition, a number of rivets have been replaced by high strength bolts.
The author has ranked this bridge as being regionally significant, due to the unique truss design and large size.
The photo above is an overview.