[3] Between 1949 and 1952, the Massachusetts Department of Public Works (MassDPW) initiated construction of the Wilbur Cross Highway extension to US Route 20 (US 20) in Sturbridge, with two lanes in each direction separated by a wide median and frequent U-turns.

In late 1968, the Federal Highway Administration (FHWA) approved a new Interstate connection from Hartford, Connecticut, to Providence, Rhode Island, which was to become part of a rerouted I-84.

On October 1, 1980, the Connecticut Department of Transportation (CTDOT) decided to truncate Route 15 back to I-84 exit 57 (where it ends today), eliminating the overlap with I-86.

When the planned portion of I-84 toward Providence ran into opposition in Rhode Island and was canceled in 1983, I-86 was officially reverted to I-84.

Plans to connect I-84 along the present day I-384/US 6 corridor from Hartford to Providence were scuttled for environmental reasons.

The Massachusetts Department of Transportation (MassDOT) planned to convert I-84, along with the rest of the state's Interstates, to use milepost-based exits during 2016;[7] however, this project was indefinitely postponed until November 18, 2019, when MassDOT confirmed that beginning in late summer 2020 the exit renumbering project will begin.