Thompson Mill Covered Bridge spans the Kaskaskia River northeast of Cowden, Illinois, and was built in 1868 as a Howe truss road bridge. Measuring 160 feet 4 inches long and only 10 feet 7 inches wide, it is the narrowest covered bridge in Illinois. It carried travelers along an important route connecting Springfield, Taylorville, and Effingham, while also providing access to Thompson Mill, a corn mill and sawmill that operated from 1843 to 1914. Built in Michigan, shipped to Shelbyville, and hauled by horse-drawn wagons to the crossing, it later earned listing on the National Register of Historic Places and survives as one of only five historic covered bridges left in Illinois.