 The portion of US 9's former routing between Waterford and Mechanicville as well as all of US 9E north of US 20 became a southward extension of US 4, which left its original alignment in Hudson Falls and followed a previously unnumbered riverside highway south to Northumberland.In between Northumberland and Mechanicville, it utilized the former routing of NY 30, which was reassigned to another highway as part of the renumbering.Virtually all of US 4 south of Hudson Falls initially overlapped other routes, all of which were assigned as part of the renumbering.