It has been 20 years since the attack on the twin towers, which took place on September 11, 2001.
The towers of the World Trade Center were struck by two hijacked planes leading to their collapse and the deaths of almost 3,000 people.
Anyone who was alive during the time can likely remember when they first saw the disturbing images coming out from the attack that changed the world forever.
But when were the twin towers first built, and at what time on 9/11 did they fall?
When were the Twin Towers built?
Construction of the World Trade Center’s North Tower began in August 1968, and the South Tower in 1969 – but plans first began after World War Two.
While the project was deemed too expensive when originally proposed in 1946, the plan was revitalised in the 1960s, spearheaded by banker David Rockefeller.
It was conceived as an urban renewal project to help revitalise the Lower Manhattan area of New York City, as well as increase the city’s role in transatlantic trade.
The iconic twin tower design itself was first proposed by architect Minoru Yamasaki when he came aboard the project in 1962.
Following construction, the first tenants moved into the North Tower in December 1970 and into the South Tower in January 1972.
The North Tower stood at 1,368 feet (417 metres), while the South Tower Center was 1,362 feet (415 metres) tall – they were the world’s tallest buildings at the time of their construction.
Four other low-level buildings were constructed as part of the World Trade Center complex in the early 1970s, and the complex was mostly complete by 1973.
A smaller seventh building – 7 World Trade Center – was opened in 1987.
What time did the towers collapse on 9/11?
During the September 11 attacks, the towers were struck by two hijacked commercial aeroplanes.
The first tower to be struck was the North Tower at 8.46 am (Eastern time, 1.46 pm UK time), collapsing almost two hours later at 10.28 am.
The South Tower was hit at 9.03 am Eastern Time, and actually collapsed first at 9.59 a.m.
The resulting debris severely damaged or destroyed more than a dozen other nearby structures, ultimately leading to the collapse of 7 World Trade Center at 5.21 pm.
The towers were eventually replaced by the One World Trade Center, which began construction in 2006 before opening in November 3 2014.
It is currently the tallest building in the US and the sixth-highest talking building in the world at standing at 1,792 feet (546.2 metres).
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