New York's Pennsylvania Station is the busiest station in the Amtrak system. 30% of all trips on Amtrak either begin or end there. Over half a million people move through Penn station every day just from Amtrak and the two commuter railroads that serve the station.
The current Penn Station occupies space underground from approximately 31st Street to 34th Street, and 7th Avenue to 8th Avenue. It is serviced by Amtrak, by the A, C, and E lines (8th Avenue subway) and the 1, 2, 3, and 9 lines (7th Avenue subway) of the NYC Subway system, the Long Island Railroad, and the NJ Transit PATH trains. It is also located directly under Madison Square Garden.
The original Penn Station was aboveground, constructed in 1910 of half a mile of pink granite quarried in Milford, Massachusetts. It featured a massive Doric colonnade along the Seventh Avenue entrance. For an idea of what it looked like, check out the James Farley Post Office building at 8th and 34th. (Side note: this is the Post Office, with the "Neither snow nor rain nor gloom of night..." motto carved in the stone across the entire entryway.) It was constructed by the Pennsylvania Railroad. The main waiting room was comparable in size to the nave of St. Peter's Basilica in Rome.
This magnificent structure was in use from 1910 until 1963, when it was torn down to build the new Madison Square Garden. Destruction of the grand old building was widely regarded as a travesty, and its destruction sparked the modern preservation movement. Senator Daniel Patrick Moynihan described it as "the great act of vandalism in the history of the city."
In 1968, the Pennsylvania Railroad merged with the New York Central to become Penn Central; the merged entity went bankrupt in 1970 and became part of the Amtrak system.
In 1998, plans to restore some of the grandeur of the old Penn Station were announced. The US Postal Service agreed to give up part of the space in the Farley Post Office building on 8th Avenue between 33rd and 34th streets to house a new -- and in some ways old -- Penn Station. The Farley Building was designed by the same architectural firm that designed the original Penn Station and built in 1914. Unfortunately, plans for the new station have been affected by the events of September 11, 2001. A Post Office located at 90 Church Street in lower Manhattan was severely damaged in the terrorist attack, and the USPS has indicated to state officials that it would not be able to give up the Farley Building as previously planned.