Known as Maryland Line Road, the highway runs 3.72 miles (5.99 km) from MD 299 and MD 313 at Massey east to the Delaware state line in eastern Kent County, where the highway continues as Clayton Delaney Road.

Maryland Line Road was improved in 1954 but was not brought into the state highway system and designated MD 330 until the late 1980s.

MD 299 heads north as Massey Road toward Sassafras, and MD 313 heads west (northbound) and south as Galena Road.

MD 330 heads east as a two-lane undivided road that immediately has a grade crossing of the Centreville Branch of the Northern Line of the Maryland and Delaware Railroad just south of the junction of the Centreville and Chestertown branches of the Northern Line.

MD 330 crosses Black Bottom Branch before it reaches its eastern terminus at the Delaware state line, where the road continues east as Clayton Delaney Road in the southwest corner of New Castle County.