Maryland Route 646
Maryland Route 646 is a state highway in the U.S. state of Maryland. Known as Prospect Road, the state highway runs from MD 543 near Ady north to MD 136 at Prospect. MD 646 was constructed as a section of MD 543 in the early 1930s. That section of MD 543 and the road originally marked as MD 646 swapped numbers by 1946.