What is now MD 273 west of Sylmar Road was improved through widening and relocations to improve curves between 1952 and 1956. MD 273 was extended west through Rising Sun to its present western terminus in 1957 when US 1 was moved to the Rising Sun Bypass. MD 273 was relocated through Calvert starting in 1956, leaving behind Brick Meetinghouse Road. The portion of MD 273 west of Octoraro Creek was transferred to county maintenance in 1959. MD 273 was realigned to a perpendicular intersection with US 1 at its western terminus in 2001. Rising Sun Road west of the intersection was retained to serve as a ramp from northbound US 1 to eastbound MD 273 and was designated MD 273A. The roundabout at the junction of MD 273 and MD 276 was constructed in 2003.