and widened from Waysons Corner to Lothian by 1946. The highway was widened from the Patuxent River to MD 416 (now MD 794) as part of intersection improvements at the MD 4–MD 416 intersection in 1950. MD 4 replaced MD 416 on Southern Maryland Boulevard and MD 408 was assigned to the old course of MD 4 between Waysons Corner and Lothian in 1965. MD 408 was relocated at its western end when MD 4 was reconstructed and the MD 4–MD 408 interchange was built in 1993. The roundabout at MD 408's eastern terminus was installed in 1995. MD 408 was also assigned to much of the old alignment of MD 4 from Meadows, a community east of Andrews Air Force Base, to the Patuxent River. The highway from Washington to Upper Marlboro was once a turnpike and, as of 1898, was the longest gravel road () in the state. The old turnpike from Meadows to the western limit of Upper Marlboro was reconstructed as a macadam road by 1915, the same year the highway from the eastern limit of Upper Marlboro to the Patuxent River was constructed as a concrete road. The portion of the highway through Upper Marlboro was built as a concrete road between 1916 and 1919. Marlboro Pike was widened with a pair of concrete shoulders and resurfaced in 1926. The road through Meadows, now Old Marlboro Pike and several roads on the grounds of Andrews Air Force Base, was bypassed along MD 4's modern alignment in 1939. Along its concurrency with US 301 through Upper Marlboro, MD 4 was widened with a pair of concrete shoulders in 1946. MD 4 was widened to and resurfaced from US 301 at Wells Corner to the Patuxent River in 1948. MD 4's freeway bypass of Upper Marlboro was built from Ritchie–Marlboro Road east to the Patuxent River between 1959 and 1962. The freeway was extended west to Dower House Road beyond the MD 223 interchange in 1964. In 1965, MD 408 was assigned to Marlboro Pike from Dower House Road to MD 223, Old Marlboro Pike from MD 223 to Upper Marlboro, Main Street through Upper Marlboro, and Marlboro Pike from Upper Marlboro to the freeway just west of the Patuxent River. These roads were transferred to county maintenance in 1977 except from Brown Station Road through Upper Marlboro to US 301; that stretch was designated MD 725