Penn South, officially known as Mutual Redevelopment Houses and formerly Penn Station South, is a limited-equity housing cooperative development located between Eighth and Ninth Avenues and West 23rd and 29th Streets, in the Chelsea neighborhood of Manhattan in New York City. The complex has 2,820 units in ten 22-story buildings. Penn South is so named because of its location southwest of New York Penn Station.

Ninth Avenue, known as Columbus Avenue between West 59th and 110th Streets, is a thoroughfare on the West Side of Manhattan in New York City, United States. Traffic runs downtown (southbound) from the Upper West Side to Chelsea. Two short sections of Ninth Avenue also exist in the Inwood neighborhood, carrying two-way traffic.