But Grand Central Terminal was about to fall victim to the same forces that originally enabled its construction.  By the early 1950's, as post-war America transformed itself into a nation of suburbs and automobiles, revenues from long-distance rail travel were plummeting.  At the same time, the value of prime Midtown Manhattan real estate had risen dramatically.  In 1954, the railroad resolved to make the most of its assets, commissioning plans to demolish Grand Central Terminal and replace it with a 6 million square foot office tower.

Nothing came of this plan.  But in 1958, the railroad concluded negotiations with developer Erwin S. Wolfson to demolish the six-story office structure at the Terminal's rear and replace it with the 59-story Pan Am Building.  Completed in 1963, the Pan Am Building sealed off Park Avenue, completely obscuring the Terminal from uptown.  Concurrently, the interior of the terminal was being parceled out for billboards and commercial advertising, in an on-going effort to increase revenues.