The portion of MD 273 west of Fair Hill was included in the planned state road system by the Maryland State Roads Commission in 1909. The planned state road continued west from MD 273's present terminus near Harrisville along the present and old alignments of US 1 to the Conowingo Bridge over the Susquehanna River. The portions of the state road between Oakwood and Octoraro Creek and from the east town limit of Rising Sun to between Sylmar Road and North East Creek were paved as macadam road in 1910 and 1911. The highway between Oakwood and the Conowingo Bridge was completed as a concrete road in 1914. The road from east of Sylmar Road to east of Calvert was under construction by 1915 and completed by 1919. Part of the gap between Octoraro Creek at Porters Bridge and Rising Sun was filled with construction of a concrete road in two stages, the first completed by 1919 and the second completed by 1921. The road from Appleton to the Delaware state line was completed as a concrete road in 1921 and 1922, and the highway from east of Calvert to east of Blue Ball was completed in 1923. The gap between Blue Ball and Fair Hill was completed by 1927, the same year US 1 was marked from the Conowingo Bridge through Rising Sun to Sylmar. The final piece of MD 273 to be paved was from Fair Hill to Appleton, which was built as a concrete road in 1929 and 1930.