MD 4 is part of the National Highway System between MD 235 in California and its northern terminus. Leonardtown to Sunderland MD 4 begins at an intersection with MD 5 (Point Lookout Road) just east of the town of Leonardtown. The highway heads east as two-lane St. Andrews Church Road. MD 4 crosses several branches of Glebe Run, including Gravelly Run, and then parallels and crosses Glebe Run. The highway crosses the Western Branch of the St. Mary's River west of Indian Bridge Road, which leads south toward St. Mary's River State Park and later becomes MD 471. MD 4 heads northeast by historic St. Andrew's Church and crosses the Eastern Branch of the St. Mary's River on its way to California, where the highway intersects MD 235 (Three Notch Road). The highway continues as Patuxent Beach Road, a two-lane controlled-access highway. The highway curves to the east and back northeast again, crossing Mill Creek and Kingston Creek before crossing Town Creek and the Patuxent River on the high-level Governor Thomas Johnson Bridge. MD 4 descends from the bridge into Calvert County just north of Solomons. The highway's name becomes Solomons Island Road and it expands to a four-lane divided highway. MD 4 has a compact interchange with MD 2, which leads south toward the Calvert Marine Museum and joins MD 4 in a long concurrency, during which the highway is often denoted MD 2–4. MD 2-4 heads north between the Solomons Naval Recreation Center to the west and MD 765 (Solomons Island Road South) on the east. MD 765 closely parallels the highway through the community of Dowell and intersections with Patuxent Point Parkway and Dowell Road. North of the latter road, MD 765 (H.G. Trueman Road) veers away from MD 2–4, which is also marked as Louis L. Goldstein Highway. MD 2-4 continues northeast through Lusby, where the highway has directional crossover intersections with Southern Connector Boulevard (unsigned MD 765Z) and MD 760 (Rousby Hall Road). MD 2-4 gradually curves north and meets the western end of MD 497 (Cove Point Road) and a connecting road that leads to the parallel MD 765 and Calvert Cliffs State Park. The highway intersects MD 765 (Pardoe Road) and receives the end of the parallel highway shortly before crossing Johns Creek. MD 2-4 is paralleled to the east by another section of MD 765, Nursery Road, as it passes to the