The southern terminus of this four-lane divided highway is at a trumpet interchange with U.S. Route 20/US 23 (US 20/US 23) approximately 3.25 miles (5.23 km) northeast of the village of Luckey.

Located entirely in the northeastern portion of Wood County, SR 420 begins at a trumpet interchange with the US 20/US 23 in Troy Township and heads due north from that point.

Immediately north of this intersection, SR 420 comes to an end as it arrives at the double-trumpet interchange that connects the route with the Ohio Turnpike, I-80/I-90.

Consequential to its function as a major connector route, the entire length of SR 420 is included within the National Highway System.

[2][3] In the fall of 2006, a new trumpet interchange was completed to facilitate traffic movement through the southern terminus of SR 420 where it meets the US 20/US 23 duplex.