Remembering 9/11: These photos recount the horror of America's worst terrorist attack

September 11, 2001 was the day that left a big dent in the history of the United States. Terror attacks in New York and Washington were visceral in their impact. In less than 3 hours, the twin towers of the World Trade Center were reduced to a mountain of twisted metal and rubble, killing more than 2,700 people, while hundreds more were killed at the Pentagon. On the 20th anniversary of the 9/11 attacks, we look back at pictures from D-Day that crippled the US.

The rubble of the twin towers of the World Trade Center smoulder following a terrorist attack in lower Manhattan, New York. Credit: AFP/File Photo

The twin towers of the World Trade Center burn behind the Empire State Building on September 11, 2001. Credit: AP/File Photo

A man covering his mouth walks through dust and debris following the collapse of one of the twin towers of the World Trade Center in New York. Credit: AFP/File Photo

A man covering his mouth walks through dust and debris following the collapse of one of the twin towers of the World Trade Center in New York. Credit: AFP/File Photo

A man stands in the rubble, and calls out asking if anyone needs help, after the collapse of the first of the twin towers of the World Trade Center Tower. Credit: AFP/File Photo

Smoke billows after the first of the two towers of the World Trade Center collapses. Credit: AFP/File Photo

A satellite image shows a closer view of the World Trade Center in New York City, New York. Credit: Maxar Technologies/Handout via Reuters

A woman covered in dust as she takes refuge in an office building following the collapse of the twin towers of the World Trade Center in lower Manhattan, New York. Credit: AFP/File Photo

Rescue workers evacuate a man through rubble and debris after the collapse of one of the World Trade Center Towers in New York. Credit: AFP/File Photo