Along the way it intersects several major highways including U.S. Route 3 (US 3) in Chelmsford, Interstate 93 (I-93) in Wilmington, I-95 in Wakefield, and US 1 in Saugus and Lynnfield.

The route then turns eastward once more, heading over the Shawsheen River into Wilmington.

Shortly after leaving the rotary, and just after crossing the Saugus River, Route 129 turns southward along Main Street, following the eastern side of Lake Quannapowitt towards the town center.

At Water Street, Route 129 turns eastward, passing the Center Depot, which is on the National Register of Historic Places and along the Haverhill Line (though currently without a stop).

Just east of this point, Route 129 enters Goodwin Circle, which provides access to all three highways via a connector road.

Immediately after leaving the circle, Route 129 enters the city of Lynn.