The first section of MD 273 east of Sylmar to be reconstructed was through Calvert, bypassing Brick Meetinghouse Road, which became MD 809. This section was built in conjunction with the relocation of MD 272 at Calvert between 1956 and 1958. The highway from east of Fair Hill to the Delaware state line was reconstructed between 1963 and 1965. As part of this work, the highway was relocated and a new bridge was built at Big Elk Creek; part of the old highway on the east side of the creek was transferred from the state to Fair Hill Training Center through an agreement on July 16, 1970. MD 273 was reconstructed from Sylmar Road to west of Calvert between 1969 and 1971. The highway from west of Little Elk Creek to east of Fair Hill was reconstructed and relocated between 1971 and 1973. The new highway bypassed Fair Hill Drive, which was transferred to the county after the new highway was completed and the old highway was resurfaced according to an October 8, 1969, road transfer agreement. The final portion of MD 273 to be reconstructed, from east of Calvert to west of Little Elk Creek, was started in 1972 and completed in 1973. MD 273's western terminus was moved to a perpendicular intersection with US 1 in 2001. The highway's roundabout with MD 276 in Harrisville was built in 2002 and 2003, the same years Main Street through Rising Sun underwent a streetscape project.