The northernmost 3 miles (4.8 km) of Route 3 is a freeway that was originally intended for the cancelled Interstate 491.

After the Silas Deane Highway (Route 99) intersection, it becomes a four-lane undivided expressway.

At an interchange with Interstate 91, it becomes a four-lane divided freeway crosses the Connecticut River on the William H. Putnam Memorial Bridge into Glastonbury.

In late 1958, as part of the planned Interstate 491 (a southeastern bypass of Hartford), a freeway from I-91 to Main Street in Glastonbury, crossing the Connecticut River on the Putnam Memorial Bridge, was opened.

In 1973, I-491 was cancelled due to local opposition and the Route 3 designation along this freeway segment became permanent.