The Hudson Line runs 74 miles north from Grand Central up to Poughkeepsie, almost entirely along the eastern edge of the Hudson River, giving this line extremely scenic views for nearly its entire route.

The line is 3rd rail electric until Croton-Harmon and diesel only the rest of the way to Poughkeepsie. In terms of service the line generally has three trains per hour or better during the day: two electric trains from Croton-Harmon one making all stops to Grand Central, and one express train making limited stops. A final train using a dual-mode hybrid diesel locomotive begins at Poughkeepsie runs local to Croton-Harmon, also stops at Ossining and Terrytown and then runs express to 125th Street and Grand Central Terminal.