U.S. Route 5 (US 5), a north–south U.S. Highway that is generally paralleled by Interstate 91 (I-91), begins at the city of New Haven in Connecticut and heads north through western Massachusetts and eastern Vermont to the international border with Canada. Within Connecticut, US 5 proceeds north from New Haven and passes through Meriden and Hartford towards Springfield, Massachusetts.

US 5 roughly follows the route used by the Upper Boston Post Road, an early colonial highway for transporting mail between New York City and Boston. The route was first improved in 1798 as the Hartford and New Haven Turnpike, which ran in a nearly straight line between the court houses of New Haven and Hartford. In 1922, the Upper Boston Post Road corridor was designated as Route 2 of the New England road marking system, crossing to the east of the Connecticut River in Hartford before continuing north to the Massachusetts state line. In 1926, Route 2 was redesignated as US 5. Several realignments have been made in the cities of New Haven and Hartford with the opening of several expressways in these areas. Because it is closely paralleled by I-91 between New Haven and Hartford, US 5 serves mainly as a secondary route today.

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