Bourne to Orleans via Sagamore and Barnstable.
Truro to Provincetown.
The western portion is the original routing of US 6. The first section to appear was between Sagamore and Barnstable, between 1950 and 1953. 1954 brought the expressway to South Dennis, near MA 134. By 1956, the Mid-Cape expressway was completed to just southwest of Orleans. US 6 took the highway; MA 6A took the old route. The Orleans bypass was complete by 1961.
The Provincetown 6A first appears on a 1956 map.