Parts of South Rolling Road were transferred to county maintenance after they were severed by the construction of I-95 and a freeway relocation of the southern end of MD 166 in the early 1970s.

MD 166 begins as a continuation of the four-lane Metropolitan Boulevard freeway at the northern terminus of I-195 just north of the Interstate's interchange with I-95.

The highway meets the western end of MD 372 (Wilkens Avenue) and passes between Rolling Road Golf Course on the east and the Catonsville Campus of the Community College of Baltimore County to the west.

MD 166 temporarily expands to four lanes between Valley Road and Bloomsbury Avenue, between which the highway passes west of Catonsville High School.

South Rolling Road crosses over CSX's Baltimore Terminal Subdivision railroad line just west of the train station.

The highway becomes an undivided, two-lane road with wide lanes and passes through residential areas in the western part of Woodlawn.

North Rolling Road continues as a four-lane undivided highway with occasional center turn lane as it passes between business parks to the east and residential subdivisions to the west.

[1][6] Several rolling roads were established in Maryland in the early 18th century for the transportation of tobacco in casks, or hogsheads, from plantations to river ports.

These casks were pulled along the road by slaves and later oxen before this method of freight transportation was made obsolete by the introduction of sturdy wagons.

[9] In St. Denis, the highway that was to become MD 166 followed modern Arlington Avenue and East Street south across a grade crossing of the B&O Railroad to its southern terminus at Washington Boulevard.