| Thomson Road–Air Line Railroad Bridge | |
| Location: | Thomson Rd. over abandoned RR right-of-way, Howard Township, Michigan |
| Coordinates: | 41.8814°N -86.1947°W |
| Architecture: | concrete T-beam |
| Added: | December 22, 1999 |
| Area: | less than one acre |
| Refnum: | 99001612 |
The Thomson Road–Air Line Railroad Bridge, also known as just the Thomson Road Bridge, is a bridge located on Thomson Road over the abandoned Michigan Air Line Railroad right-of-way in Howard Township, Michigan. It was listed on the National Register of Historic Places in 1999. It is one of the oldest examples of a concrete T-beam bridge in Michigan, and has a rare brick deck.
The main line of the Michigan Central Railroad, located about west of this site, was constructed through Cass County in 1848.[1] Just after the Civil War, a new rail line known as the Michigan Air Line Railroad was constructed, linking Jackson with the Michigan Central line at Niles; two years later, the route was controlled by the Michigan Central. In 1919, a cutoff was constructed through Howard Township, linking the main Michigan Central line to the Airline. This bridge was constructed at the same time, probably from a design developed by the railroad company.
The railroad beneath the bridge has been abandoned for many years and is overgrown.[1]
The Thomson Road–Air Line Railroad Bridge is one of the oldest examples of a concrete T-beam bridge in Michigan, and the only historically significant bridge of the type having multiple spans.[1] The entire bridge is long and just over in width, with five spans of in length. The length of the structure is due to the wide right-of-way beneath, which was used as a railroad switchyard known as the "Hump." The bridge has an unusual brick deck,[2] which has a slight arch.[1] The original bridge railings are metal pipe panels strung between concrete posts. The bridge has maintained an excellent integrity.