Route 25 is a six-lane freeway from Bridgeport to northern Trumbull and a two-lane surface road the rest of the way to Brookfield.

The Route 25 designation was assigned in 1932 to the turnpike alignment and additionally extended through New Milford all the way to Torrington.

The freeway section ends at the junction with Route 111 on the northern edge of town.

The planned 9-mile (14 km) extension was canceled in 1991, along with many other highway projects due to a fiscal crisis arising when Connecticut was especially hit hard by the Late 1980s recession.

[4] During the late 1990s, an alternative plan to widen the existing Route 25 to 4 lanes with a center turn lane in certain spots through Trumbull, Monroe, and Newtown was met with opposition, particularly in Newtown where there was strong opposition to any type of project that will change the existing profile of the Route 25 corridor, despite the high accident rate and congestion on the road.

In the early 2000s the Connecticut Department of Transportation (ConnDOT) was forced to resort to a plan that will widen and improve intersections on Route 25 from the freeway terminus in Trumbull to the Monroe/Newtown town line, but opposition in Newtown has compelled ConnDOT to limit upgrades in that community to spot improvements at major intersections and routine maintenance and periodic rehabilitation or replacement of existing bridges and culverts without adding capacity to the road.

To ease traffic congestion in Newtown, ConnDOT opened the Mile Hill Road Bypass (SR 860), cutting through the former Fairfield Hills Hospital property and connecting to I-84 and Route 34 at the freeway stub originally intended for Route 25 (now part of SSR 490).

ConnDOT is also planning to build a rest area on land left over when the interchange conversion is complete.