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.

Cowlitz County is a county located in the U.S. state of Washington. As of the 2020 census, its population was 110,730. The county seat is Kelso, and its largest city is Longview. The county was formed in April 1854. Its name derives from the anglicized version of the Cowlitz Indian term Cow-e-liske, meaning either 'river of shifting sands' or 'capturing the medicine spirit.' Cowlitz comprises the Longview, WA Metropolitan statistical area, which is also included in the Portland-Vancouver-Salem, OR-WA Combined statistical area.