Since the mid-1980s, several suffixed sections of MD 18 have been created, relocated, or received new designations due to expansion of US 50/US 301 to a freeway.

MD 18A runs 5.39 miles (8.67 km) from Love Point south and east through Stevensville to a roundabout at Castle Marina Road in Chester.

MD 18B extends 7.94 miles (12.78 km) from the same roundabout east through Chester, Kent Narrows, and Grasonville to US 50 in Queenstown.

After meeting Old Love Point Road at an acute angle, MD 18A passes suburban subdivisions and Kent Island High School.

MD 18B continues around the south end of Piney Creek before entering the hamlet of Kent Narrows, where the highway has a direct connection to eastbound US 50/US 301.

The state highway also has an indirect connection to the westbound freeway via Piney Narrows Road, where it passes south of a park and ride lot under the freeway serving MTA Maryland commuter buses, immediately before crossing Kent Narrows on a drawbridge adjacent to the US 50/US 301 crossing of the strait.

The state highway continues through farmland before reaching its eastern terminus at US 50 (Ocean Gateway) just east of the US 50 – US 301 split in Queenstown.

At the intersection with MD 656 (Friels Road) and Outlet Center Drive, which heads into the Queenstown Premium Outlets, the state highway turns north and reaches its eastern terminus at a superstreet intersection with US 301 (Blue Star Memorial Highway).

The state highway passes the namesake park of the youth agricultural organization shortly after crossing Reed Creek.

[1][5] The first sections of MD 18 was paved as three separate state-aid roads within Queenstown and Grasonville by 1915, and between Stevensville and Chester shortly after 1915.

[12] The east–west highway between Stevensville and Queenstown was finished with the completion of a timber trestle bascule bridge over Kent Narrows.

[15] The US 50 divided highway started construction in 1950 and was completed between the Chesapeake Bay Bridge and Queenstown in 1952, including a new drawbridge over Kent Narrows.

The upgrade included a new fixed high-level bridge over Kent Narrows for US 50/US 301, relegating the 1952 drawbridge to be used only by MD 18.

Access to eastbound US 50 would be via a new service road south of US 50 and connections with westbound US 50 would be made through Outlet Center Drive.