State Route 4 (SR 4) is a 62.27-mile-long (100.21 km) state highway, serving the southwestern region of the U.S. state of Washington. The highway, also known as Ocean Beach Highway, travels east along the Columbia River from U.S. Route 101 (US 101) at Johnston's Landing through Pacific, Wahkiakum and Cowlitz counties to an interchange with Interstate 5 (I-5) in Kelso. SR 4 is designated as part of the Lewis and Clark Trail Scenic Byway, a state scenic byway, as well as part of the National Highway System.

Wahkiakum County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 4,422, making it one of the least populous counties in Washington. The county seat and only incorporated town is Cathlamet. The county was formed out of Cowlitz County in April 1854 and is named for Chief Wahkiakum of the Chinook, who is buried in the Pioneer Cemetery in Cathlamet.