State Route 409 (SR 409) is a short Washington state highway in Wahkiakum County. The highway runs north from the Wahkiakum County Ferry on Puget Island to SR 4 in the county seat of Cathlamet over a distance of 3.84 miles (6.18 km). The route connects Westport, Oregon, which is served by the county ferry, and Cathlamet. The highway was referred to as Secondary State Highway 12F (SSH 12F) from 1943 until 1964.