Shortly after crossing the highway, Route 133 enters Essex County and the town of Andover.

The route passes through the village of West Boxford before continuing into Georgetown.

In Ipswich, the two routes cross the Newburyport Line railroad tracks as it enters the downtown area.

The two routes cross the historic Choate Bridge over the Ipswich River concurrently, before turning southward, passing through the historic village before splitting once more, with Route 133 heading east-southeastward into Essex.

Between 1959 and 1961, it was extended to replace what was MA Route 121 (which existed from Ipswich to Gloucester via Essex).