The 1953 Pennsylvania Railroad train wreck occurred on January 15, 1953, when a passenger and mail train from Boston to Washington DC (the Federal) failed to brake sufficiently on its approach to Union Station, Washington, jumping the platform and plunging through the floor of the concourse.

The cause of the accident was a design flaw that allowed an air brake valve to close without human intervention.

Conductors discovered a closed "angle cock" (an air shutoff valve) at the rear of the third car.

The engine supplies air pressure that is supposed to flow through the airbrake system along the entire length of the train.

[2] A routine inspection during the train's stop in New York City, inspectors later said, found the angle cock in the correct, open position.

[2] But an after-accident investigation by the ICC revealed that the handle of the angle cock at the rear of the third coach was not in the correct position, as a design flaw on New Haven coach #8665 allowed the handle of the angle cock valve to come into contact with the coupler, causing the valve to close.

It had slowed to just 35 miles per hour (56 km/h) when it struck the bumper (the steel barrier at the end of the track).

[5] The floor, not designed to hold the weight of a train, gave way beneath the 475,000 lb (215.5-tonne)[7][8] locomotive, and the rear of the engine plunged into the baggage and mail rooms in the basement below.

A Life magazine photo showed the nose of the engine just pushing open the doors to the waiting room.

[1] The stationmaster's clock, which was found in the wreckage, showed the time frozen at 8:38 a.m.[1] NBC News was able to broadcast live from Union Station just 67 minutes after the wreck occurred.

[5] The railroad called in a local contractor, Steiner Construction Co. of Baltimore to assess the damage and make temporary repairs.

As the incident occurred just five days before the inauguration of Dwight D. Eisenhower as the 34th President of the United States, it was decided to make temporary repairs to accommodate the expected crowds.

Working round the clock, the derailed cars were removed, the engine lowered into the basement, and Steiner Construction erected a temporary wooden floor over the hole in the concourse and covered it with quick-drying asphalt in just two days.

[5] The workers also built a temporary station master's office and newsstand in time for the crowds coming in to DC.

After new frames were ordered and a replacement superstructure fabricated, any components that were able to be reused went towards what was essentially a new 4876 that remained in service for another 30 years.