Expanding the train station, the busiest in the nation, is a pressing issue because construction has just begun on a $16 billion pair of rail tunnels under the Hudson River, the centerpieces of a project known as Gateway, which would double the current cross-Hudson capacity.

Under the plan by the Grand Penn Community Alliance plan, Penn Station will move above ground while Madison Square Garden is relocated.

In the ensuing years, the city transformed, and with it the way people traveled. By 1962, it seemed like a good idea to put an entertainment arena where the above-ground station had been for just over 50 years. Enter Madison Square Garden, above, and Penn Station, as we know it now, underground.