MD 63 was originally assigned to Spielman Road between Spielman and Williamsport. The portion of the highway from Williamsport north to Cearfoss was originally MD 398, which was the descendant of the 19th century Williamsport and Greencastle Turnpike. MD 63 was paved from the Norfolk and Western Railway at Spielman west to Downsville in 1916. Spielman Road was paved from Downsville to Williamsport in 1933. MD 63 originally had its northern terminus at MD 68 at the southern town limit of Williamsport, now the corner of Artizan Street and Sunset Avenue. MD 68 followed Sunset Avenue from the direction of Lappans to the MD 63 junction, then turned north along Artizan Street to its northern terminus at US 11. MD 398 was paved from US 11 to the branch of Conococheague Creek just south of present-day I-81 in 1930. Greencastle Pike was constructed to Cearfoss by 1933.