By the middle of the 19th century, there was a railroad, the Hudson (later West Side) Line, running from the current Hudson Yards area between 30th and 32nd Streets south to Chambers Street. At the time, the city prohibited steam locomotives from operating below 30th Street because of the risk of the train's steam boiler exploding, so passengers from points north were forced to switch to horse-drawn trains. The horse-drawn line's stops were located at 23rd, 14th, Christopher and Chambers Streets.