U.S. Route 5 (US 5), a north–south United States Numbered 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 toward Springfield, Massachusetts.

North of Meriden, it becomes a four-lane arterial road known as the Berlin Turnpike, where a long overlap with Route 15 also begins.

US 5 continues through the southern suburbs of Hartford along the Berlin Turnpike, shifting just south of the city line to the Wilbur Cross Highway, a freeway.

US 5 roughly follows the route used by the Upper Post Road, an early colonial highway for transporting mail between New York City and Boston.

Because it is closely paralleled by I-91 between New Haven and Hartford, US 5 serves mainly as a secondary route today.

US 5 then turns right at the intersection with Bishop Street in North Haven and crosses the Quinnipiac River, the railroad tracks, and I-91 (at exit 11) overlapped with Route 22 on a four-lane wide road.

The four-lane Washington Avenue runs through the commercial areas of North Haven still paralleling the railroad tracks, crosses under I-91 (at exit 12) and continues into Wallingford as South Colony Street.

At the town line is Wharton Brook State Park, just north of SR 702, a short freeway that provides access to I-91.

[1][2] At the merge with Route 150 just before the town line, US 5 then follows South Broad Street (the alignment of the old Hartford and New Haven Turnpike) into the city of Meriden.

About half a mile (0.80 km) further north, US 5 has an interchange with I-291 (at exit 4) that also includes access to Route 30, the main road to the South Windsor town center.

About half a mile (0.80 km) north of this junction, US 5 leaves Main Street to go on Prospect Hill Road, bypassing the Warehouse Point area.

[1][4] The Upper Post Road was established in 1673 between New York City and Boston via New Haven, Hartford, Springfield, and Worcester.

North of Hartford, the road remained on the west side of the Connecticut River, following the general path of present Route 159.

This route crossed the Quinnipiac River in New Haven, heading north along an old road (now Route 103 and US 5) to Tracy, crossing the turnpike and running through downtown Meriden on Old Colony Road, Cook Avenue, and Colony Street.

[16] In Hartford, the original alignment of US 5 entered the city on Maple Avenue and made its way to the Bulkeley Bridge via Main Street, Central Row, and Columbus Boulevard.

In East Hartford and South Windsor, a new four-lane expressway, John Fitch Boulevard, was also constructed.

[20] In 1948, Route 15 was designated on the Berlin Turnpike and Hartford Bypass segments of US 5 in order to connect the Merritt Parkway and Wilbur Cross Parkway to the Wilbur Cross Highway, providing a continuous high-speed route between New York and Massachusetts.

In the case of US 5, most of its non-expressway alignment except for the Berlin Turnpike has been given a commemorative designation by the Connecticut General Assembly over the years.