The S Bridge is located about four miles east of Old Washington, just north of the current alignments of Interstate 70 and County Road 690.

The main span is a segmented stone arch, whose crown is typically 18 inches (46 cm) above the streambed.

The bridge is built out of randomly laid ashlar stone, which rises to low parapets giving a roadway width of 26 feet (7.9 m).

The bridge's characteristic S shape is derived from the sharply curving approaches on either side of the main span.

This bridge was built as part of that expansion project, and was the major route by which Ohio and the Old Northwest were settled.