MD 23 is an L-shaped highway in northwestern Harford County that consists of two major sections.

After crossing over Bynum Run and the Ma and Pa Trail, a rail trail along the abandoned right-of-way of the Maryland and Pennsylvania Railroad, MD 23 intersects MD 24 (Rocks Road/Rock Spring Road) just south of Forest Hill.

The state highway makes a sharp, curvaceous descent to a crossing of Deer Creek, next to which is the historic Ivory Mills complex located east of the road.

MD 23 turns west and closely parallels the state line for about 2,000 feet (610 m) before the highway veers northwest to cross the border.

The highway continues north as PA 24 (Barrens Road) toward the borough of Stewartstown.

[12][13] The MD 23 designation was moved to the new highway and Jarrettsville Road was immediately transferred to county maintenance.

[13] At its eastern end, East–West Highway was constructed to tie into the Bel Air Bypass that was completed in 1965 and was proposed to continue to east of Hickory.

[14] Close to its eastern end, MD 23 curved south to an intersection with Granary Road.

MD 23 turned east onto Granary Road for its eastern terminus at US 1 (now US 1 Business).

As part of the same project, MD 23 was extended east to a new terminus at the Hickory Bypass.