Thompson Mill Covered Bridge, Cowden Illinois

Date added: February 19, 2024 Categories: Illinois Covered Bridges Howe Truss
South end of bridge looking north (1973)

The covered bridge was erected in 1868 in the vicinity of the Thompson Mill from which it derives its name. The bridge was fabricated in Michigan, shipped to Shelbyville, and was transported from there to the job site by horse-drawn wagons. The road on which the bridge was constructed, served as a major route from Springfield to Taylorville to Effingham, all in Illinois.

It also provided access from the local residences and farms to the Thompson Mill and other communities. The bridge is the narrowest of the remaining eight covered bridges in Illinois, being only 10' 7" wide. A small community of log houses flourished there, but are no longer in existence.

The Thompson Mill, constructed in 1843, was located upstream from the covered bridge. It supplied a much-needed service to the surrounding area as a corn and saw mill. The Mill was destroyed and rebuilt in 1872 and remained in operation until 1914 when it was torn down. The remains of the old dam can still be seen from the bridge.

The covered bridge represents one of the few remaining vestiges of a type of construction utilized in Illinois during the 19th century horse and buggy days. One reason given for Covered Bridge Construction is that the bridges were built to resemble a barn to keep the horses from shying at the running water.

Bridge Description

A covered bridge with two steel "I" beam approach spans on each end and the covered span in the center. The Covered span is constructed of wood with through Howe trusses for main support. The Covered span is 103 feet 4 inches center to center of piers, with an overall length of 160 feet 4 inches. The horizontal clearance on the roadway is 10 feet 6 inches and vertical clearance is 11 feet 8 inches. The original timbers are still intact with the roof and siding restored.

The covered bridge was erected at the job site in 1868. At the time all members were constructed of wood and timber including the flooring. The bridge was set on two sets of piers consisting of 5 tubular iron shells each filled with shale. It appears that the steel "I" beam approaches were added sometime later and the ends were set on timber abutments and piling. Except for replacing one or two diagonal cross pieces in the truss, because of rot, and making minor repairs capping the metal piers with concrete, the Howe Truss and the iron shells are original construction. The roof and siding have been repaired several times since the bridge was erected the last time being about 1966-67, by State Highway Day Labor Forces. Most of the floor planks have probably been replaced over the years due to wear. The structure had mismatched steel railing along the sides of the approaches. During 1973 this was replaced by a rustic wood railing and the steel "I" beam members under the approaches were painted a color to res wood to restore the original appearance of the structure.

The Howe Truss consists of a series of panels formed by vertical iron tension rods and 2 diagonal wooden compression members that form an X between the rods.

Thompson Mill Covered Bridge, Cowden Illinois South end of bridge looking north (1973)
South end of bridge looking north (1973)