Tunnel No. 1 is located on the former Cincinnati, Hamilton & Dayton Railroad Ironton Branch near Hoadley, Ohio.
Tunnel No. 1, completed in 1882 by the Toledo, Cincinnati & St. Louis Railroad (TC&StL), 3 featured a brick lining. The TC&StL was acquired by the Cincinnati, Hamilton & Dayton Railroad (CH&D) in 1891 and became the Ironton Branch.
In 1916, under the CH&D, work commenced on improvements to the tunnels along the Ironton Branch but flooding later in the year washed out substantial portions of the CH&D south of Wellston. The railroad opted to abandon the route from Wellston to Dean Junction, including tunnels No. 1, No. 2, and No. 3. 1 2
- State: Ohio
- Route: Cincinnati, Hamilton & Dayton Railroad
- Type: Tunnel
- Status: Abandoned / Closed