 Alt US 40 runs from Keyser's Ridge to Cumberland, following part of the route of the National Road through some of Maryland's most mountainous terrain in Garrett and Allegany counties.The highway is a part of the National Highway System as a principal arterial from the eastern junction with MD 36 in Frostburg to the intersection of Mechanic Street and Henderson Avenue in Cumberland.Alt US 40 branches from US 40 near exit 14 on I-68 at Keysers Ridge.