Stunning images of the New York City skyline every year on 9/11

At around 1,360 feet each, the Twin Towers were a prodigious feature of the Manhattan skyline.

As the smog began to lift, New Yorkers were confronted with the glaring disappearance of the Twin Towers, a structural duo that had become synonymous with the city itself.

Mourners gathered at Ground Zero for a memorial service on the first anniversary of the attacks. For two and a half hours, officials recited the names of the victims against a backdrop of orchestra music.

New York City commemorates the attacks each year by casting 88 searchlights into the sky, creating two columns of light to represent the Twin Towers. The installation, known as Tribute in Light, started on the first anniversary of 9/11 and has since become an annual memorial. 

President George W. Bush held a moment of silence on the White House lawn on the third anniversary of the attacks.

Construction at the site was in full swing.

Construction of the "Reflecting Absence" memorial began in 2006.

Members of the public deliver remarks at the service.

Bush attended the dedication of the 9/11 Pentagon Memorial in 2008.

"The Pentagon Memorial will stand as an everlasting tribute to 184 innocent souls who perished on these grounds," he said in his remarks. "The benches here bear each of their names. And beneath each bench is a shimmering pool filled with the water of life — a testament to those who were taken from us, and to their memories that will live on in our hearts."

Construction also continued on the 9/11 Memorial and Museum. The first artifact, a 36-foot steel beam known as  the "Last Column," was moved from conservation to the museum in 2009.

In 2010, the Survivor Tree was replanted at the site. The Callery pear tree was found damaged in the aftermath of the attacks.

Since 2011, politicians have not been allowed to read names or deliver remarks at the 9/11 commemoration service in order to preserve the apolitical nature of the ceremony. 

President Barack Obama spoke at the Pentagon Memorial Service in 2012.

"This anniversary allows us to renew our faith that even the darkest night gives way to a brighter dawn," he said. "Today, we can come here to the Pentagon, and touch these names and kneel beside a building where a single stone still bears the scars of that fire."

The Freedom Tower, visible in the background, had not yet been officially unveiled.

As New Yorkers gathered for another year of memorial services, Obama delivered a speech at the Pentagon in Washington, DC.

"Beginning tomorrow, there will be teenagers — young adults — who were born after 9/11," Obama said. "While these young Americans did not know the horrors of that day, their lives have been shaped by all the days since."

The Tribute in Light shines from West and Morris streets, south of the World Trade Center.

Then-presidential candidates Donald Trump and Hillary Clinton attended the memorial ceremony.

President Donald Trump delivered remarks at the Pentagon's 9/11 memorial service.

"We're gathered here today to remember a morning that started very much like this one," he said. "On that day, not only did the world change, but we all changed. Our eyes were opened to the depths of the evil we face. But in that hour of darkness, we also came together with renewed purpose. Our differences never looked so small, our common bonds never felt so strong."

A fourth building, 3 World Trade Center, opened on June 11, 2018.

One World Trade Center and the re-developed area where the Twin Towers of World Trade Center once stood in New York City are visible in the background.

The beams of light lit up the clouds above.