The Castleton Subdivision is a railroad line owned and operated by CSX Transportation in the U.S. state of New York. The line runs from Schodack northwest to Selkirk along a former New York Central Railroad line. At its southeast end, it junctions with the Berkshire Subdivision and Schodack Subdivision. After crossing the Hudson River on the Alfred H. Smith Memorial Bridge, it meets the River Subdivision and Port Subdivision at Selkirk and ends at Selkirk Yard, where the Selkirk Subdivision begins.