New York State Route 421 runs east-west in Southeastern St. Lawrence County. It runs just over five and a half miles. NY St Rt 421 passes through the following town in St. Lawrence County. Piercefield NY St Rt 421 is not multi-plexed in St. Lawrence County. NY St Rt 421 intersects the following highway in St. Lawrence County. New York State Route 30, at Piercefield.
