At the end of 1926, the U.S. Highway system was established and several of the primary New England routes were redesignated as U.S. routes. New England Route 28 was not renumbered but New England Route 1 became U.S. Route 1; New England Route 6 became U.S. Route 3 north of Boston and mostly State Route 3 south of Boston; and New England Route 3 became mostly U.S. Route 6. In Cape Cod, however, this was not the case. Former New England Route 3 was assigned as a southern extension of Route 28, while former New England Route 6 was assigned as an eastern extension of U.S. Route 6.