It heads southeastward up the valley of the Stevens Branch of the Winooski River, passing through the northeastern corner of the town of Berlin and entering Barre, where it becomes North Main Street.

In the center of Barre, US 302 becomes Washington Street at the junction with Vermont Route 14 south, and continues southeastward up the valley of the Jail Branch River.

The highway turns northeastward, passing through a corner of Topsham, crosses another height of land, and enters the valley of the Wells River in the rural town of Groton.

The highway turns southeastward again, following the Wells River and passing through the village of South Ryegate, before intersecting Interstate 91 in the northern part of the town of Newbury.

It follows Central Street on a two-lane alignment, passing through Woodsville until it reaches NH 10 (Dartmouth College Highway), where it turns eastward.

The highway passes the north end of Jordan Bay on Sebago Lake in the town of Raymond, and crosses the Pleasant River at milepost 13.4 in Windham.

The highway eliminated railway passenger travel over the route from Portland by 1958, and railroad freight service through Crawford Notch was discontinued in 1983.

[8] From 1922 until 1935, much of what is now US 302 was a part of the New England road marking system, designated as Route 18, from Portland, Maine, northwest to Littleton, New Hampshire, roughly 112 miles (180 km).