Upon entering the Hudson city limits, NY 9G and NY 23B change from a state-maintained highway to a locally maintained street as it traverses the marshy South Bay. The routes continue into the commercial downtown district, where they follow Third Street for several blocks to Columbia Street. Here, NY 9G and NY 23B veer east, following Columbia Street through the city to a junction with US 9 at Park Place. NY 9G terminates here; however, NY 23B continues east on Columbia Street, now joined by US 9. Both routes curve onto Green Street one block later. At Fairview Avenue, US 9 splits from NY 23B and heads north while NY 23B heads southeastward as an independent route for the first time. NY 23B passes out of Hudson and back into Greenport after intersecting the southern terminus of NY 66 at Columbia Street.