The Mill Creek Expressway generally follows the old Miami and Erie Canal, which extended from Cincinnati to Toledo via Dayton, itself built in the Mill Creek valley near Cincinnati. The canal extended from the Ohio River along the present locations of Eggleston Avenue and Central Parkway to Mt. Storm Park, and continued north, remaining close to the Mill Creek Expressway to Butler County. The never-opened Cincinnati Subway was built in the 1920s, mostly using the abandoned canal right-of-way from downtown to the State Route 562 interchange at St. Bernard.