MD 63 is an L-shaped route that passes through central Washington County on the south and west sides of Hagerstown.

MD 63 crosses a one-lane bridge over Marsh Run just prior to Reichard Road; makes a sharp turn to the south adjacent to Marsh Mills; makes another sharp turn to the west; crosses a one-lane bridge over St. James Run; and crosses Norfolk Southern Railway's Hagerstown District line at-grade in the hamlet of Spielman.

At the north town limit of Williamsport, state maintenance resumes and MD 63's name changes to Greencastle Pike.

The old alignment of MD 63, Honeyfield Road, parallels the state highway on the west as the highway enters a mix of farmland, forest, and industrial properties and crosses over Semple Run and CSX's Lurgan Subdivision railroad line.

[1][2] MD 63 continues north as a two-lane undivided highway past several industrial parks and farms before intersecting US 40 (National Pike) in the village of Huyett, where the highway is paralleled by the old alignment, Huyett Lane, to the east.

The state highway starts to curve to the northeast through farmland, crossing Rush Run and intersecting Broadfording Road before approaching the village of Cearfoss.

[3][4] MD 63 was paved from the Norfolk and Western Railway at Spielman west to Downsville in 1916.

[12] Reconstruction and relocation of the highway from the northern limit of Williamsport to a short distance north of US 40 in Huyett began in 1957.

MD 68, which had been extended west to Clear Spring in 1956, was relocated south of Williamsport, replacing Sunset Avenue and what is now Kendle Road, in 1965.

[16][17] MD 68 was relocated for a grade separation of the Cumberland Valley Railroad and to tie into an interchange with I-81 and the south end of Conococheague Street.