Between Kittery and South Berwick, SR 236 is known as the Harold L. Dow Highway.

The highway runs roughly parallel to the New Hampshire border (the Salmon Falls River) over its entire length.

SR 236 has partial interchanges with US 1 Bypass and I-95, then continues northwest along the former right-of-way of the B&M Railroad until intersecting SR 4 in South Berwick at the northern end of the Dow Highway.

SR 236 is cosigned with SR 4 in downtown South Berwick, then splits off to follow Berwick Road into downtown Berwick along Allen Street to its northern terminus at SR 9 (School Street), approximately 1,200 feet (370 m) east of the New Hampshire state line.

That route was truncated to its current terminus in 1957, and its northern segment was re-designated as SR 236.