It was late in the afternoon on a beautiful spring Saturday - March 25, 1911 - 4:40 p.m., to be exact.

It was nearly quitting time at the Triangle Shirtwaist Factory in New York's Greenwich Village, where 500 workers, mostly young Italian and Jewish women and girls, got ready to collect their pay, and go home.

Someone dropped a match, or a cigarette ... and within minutes the factory, which occupied the top three floors of a 10-story building, became an inferno.

Photos: The 1911 Triangle Fire Tragedy

Fire ladders, which reached only 6 floors up, were useless. The fire escape collapsed under the weight of desperate workers trying to escape.

One of the doors, it would be reported, was locked.

Onlookers, out for a weekend stroll in nearby Washington Square Park, watched in horror as women leapt to their deaths from upper-story windows , some crashing through the firemen's nets, others hitting the sidewalk with a sickening thud.

That terrible day 100 years ago was almost a mirror of 9/11, said Michelle Miller.

"In some ways it was," said researcher Michael Hirsch. "The horror of the fire, jumping the way they did. It was more intimate, though. You could look into their faces, see the expression on their face in their last moments, hear them hit the pavement that way."

In the days that followed, family members crowded into a makeshift morgue, trying, sometimes in vain, to identify those they lost among the charred remains.

On that day, says Hirsch, all of New York was united in grief.
Read more: Remembering an American tragedy - CBS Sunday Morning - CBS News