This ridge separates several sets of watersheds in central Maryland, with the result that MD 27 bridges no significant streams.

The highway becomes two lanes again at the west end of downtown Damascus, curves east then turn north to remain on Ridge Road.

[1][6] MD 27 starts of Damascus as a four-lane undivided highway but quickly drops to two lanes.

The highway crosses the Patuxent River just south of its source and passes through the western edge of Howard County.

The highway meets the west end of the Mount Airy–Ellicott City segment of MD 144 (Old National Pike).

[1][6] Parrs Spring contains the quadripoint where the boundaries of Montgomery, Howard, Frederick, and Carroll counties meet.

MD 27 intersects a non-state segment of the old road, Westminster Street, shortly before the route enters the town of Manchester and passes south of a park and ride lot before reaching its northern terminus at MD 30 (Hanover Pike), the town's main street.

[12] The northernmost part of the highway, a concrete road along Westminster Street in the town of Manchester, was completed by 1921.

[14][13] The concrete road was started from the Westminster end and reached a point north of Warfieldsburg by 1923.

[17] Ridge Road was completed from Mount Airy to Westminster when the gap through Taylorsville was filled in 1929.

[20] MD 27 was widened with the addition of a pair of 2.5-foot-wide (0.76 m) and resurfaced from Damascus to Ridgeville and from Mount Airy to the north of Dorceytown in 1938.

[23] The highway between Cedar Grove and Damascus was widened and resurfaced in 1953 and 1954; this work included a major relocation that replaced a curvaceous segment on what is now Oak Drive.

[24][25] Modernization of MD 27 between Germantown and Mount Airy concluded when the portion between US 240 and Cedar Grove was widened and resurfaced between 1954 and 1956.

[23] MD 27 was widened and resurfaced from Westminster to the south of Warfieldsburg between 1950 and 1954; this work included a relocation at Spring Mills.

[22][24][27] Work on the highway from south of Warfieldsburg to Taylorsville and there to Mount Airy; both widening and resurfacing projects got underway in 1954 and were completed in 1956.

[28] This project involved several relocations of the highway, including moving Manchester Road to its present terminus at MD 30, by the time it was completed in 1960.

[29] MD 27's original interchange with I-70 was constructed when US 40 was relocated as a four-lane divided highway through Ridgeville in 1953 and 1954.

[34][35] This work was part of a state– county project to connect Ridge Road and Father Hurley Boulevard with I-270 to improve access between I-270, Germantown, and Damascus.