Now in the town of Nassau, NY 66 continues northeast along Kinderhook Creek, soon reaching a junction with US 20. Continuing to parallel Kinderhook Creek, US 20 and NY 66 form a concurrency through Nassau, passing several former alignments of US 20 before crossing over the creek twice. Rapidly approaching the Columbia County line once again, the routes reach the residential hamlet of Brainard, where they meet the northern terminus of CR 19, a short connector the aforementioned Columbia CR 13. Just east of this junction, NY 66 forks north off US 20 and continues north along Kinderhook Creek as it enters the village of East Nassau.