After the September 11, 2001 attacks, when the smoke finally cleared and the last of the wreckage was removed, the long road to rebuilding the 16 acres of the World Trade Center began, resulting in what is still one of the biggest infrastructure projects in the world, with thousands of workers involved. Here are some official—and unofficial—milestones:

November 2001: The Lower Manhattan Development Corporation was created "to help plan and coordinate the rebuilding and revitalization of Lower Manhattan, defined as everything south of Houston Street."

July 2002: Proposed designs for the new World Trade Center site flop and so officials ask for more designs.

Daniel Libeskind's Freedom Tower design (dbox)

February 2003: After narrowing in on finalists, Daniel Libeskind's design for the World Trade Center site is selected by the Lower Manhattan Development Corporation. Governor Pataki calls the building "Freedom Tower."

July 2003: Santiago Calatrava is selected as the designer of the new World Trade Center transit hub.

December 2003: A revised design for the Freedom Tower, by Libeskind and David Childs, was released.

Construction at the World Trade Center site in March 2003 (Getty Images)

January 2004: After a public competition, a design for the 9/11 Memorial, by Housing Authority architect Michael Arad and landscape architect Peter Walker, was selected by the LMDC.

July 2004: The cornerstone is placed at Ground Zero during Freedom Tower's official groundbreaking.

Mayor Michael Bloomberg unveils a cornerstone's inscription as New York State Governor George Pataki and New Jersey Governor James McGreevey look on on July 4, 2014 (Getty Images)

May 2005: The design for Freedom Tower gets scrapped over security concerns.

Norwegian design firm Snohetta presents the design for the World Trade Center Culture Center, which ends up being the 9/11 Museum. Donald Trump suggests rebuilding the original World Trade Center.

June 2005: Freedom Tower is redesigned by Childs into its current state (except for the cladding around the spire). Here's a good graphic showing the evolution of design.

April 2006: Construction on Freedom Tower, now called simply 1 World Trade Center, begins. Developer Larry Silverstein and the Port Authority agree on a deal over control at the site.

May 2006: Seven World Trade Center opens. There's also lots of cost-cutting overall.

7 World Trade Center is the only skyscraper completed as of January 2006 (Getty Images)

September 2006: Plans for the three other buildings at the site, Towers 2, 3 and 4, are revealed, designed by a starry array of international architects.

October 2006: Remains of 9/11 victims are found at Ground Zero, upsetting victims' families who think construction is being rushed by elected officials.

May 2007: Silverstein gets a total of $4.55 billion in insurance payouts to complete/continue building at the site.

September 2008: Downsized designs for the 9/11 Memorial and Museum are presented.

June 2009: Construction workers at Ground Zero are spotted enjoying liquid lunches. (And seen again two years later.)

February 2010: Silverstein threatens to dump plans to build Tower 2.

Summer of 2010: Ground Zero Mosque becomes a thing—and it's not even at Ground Zero—to test New Yorkers' tolerance. Thanks, Sarah Palin.

August 2010: Trees are planted at the 9/11 Memorial site as Conde Nast is rumored to move to the future One World Trade Center.

Crowds gather at Ground Zero after hearing that Osama bin Laden has been killed.

May 2011: Crowds flock to Ground Zero to celebrate the death of Osama bin Laden.

Also, testing on the 9/11 Memorial's waterfalls begins and Conde Nast officially signs a lease for 1 WTC.

September 2011: The 9/11 Memorial opens on the 10th anniversary of the September 11 attacks.

The South Pool, looking north towards the museum entrance. (Compare the difference from April 2010 and June 2011) (Jake Dobkin / Gothamist)

January 2012: One World Trade Center has the dubious distinction of being the most expensive building in the world.

April 2012: One World Trade Center is officially taller than the Empire State Building.

September 2013: A trio of BASE jumpers dove from 1 World Trade Center; video of their escapade was widely viewed in March 2014 after their arrest.

January 2013: Construction on Tower 3 gets caught in the quagmire that is the agreement between the Port Authority and Silverstein. After initially thinking that it would be complete by 2015, 3 World Trade Center, designed by Richard Rogers, is now on track to open in 2018.

April 2013: Pieces of a plane that crashed into the World Trade Center were found wedged between buildings a few blocks northwest of the site.

October 2013: During his month-long residency in NYC, British street artist Banksy created a Twin Towers tribute piece and, two weeks later, stated that One World Trade Center sucks and it should be replaced with better artwork.

Nic Garcia / Gothamist

November 2013: One World Trade Center is officially considered America's tallest building. Tower 4, a.k.a. Four World Trade Center, designed by Fumihiko Maki, opens.

March 2014: A 16-year-old NJ boy managed to sneak through security to the top of One World Trade Center. The head of security soon resigns.

May 2014: President Obama dedicated the 9/11 Museum. The day after, I got kicked out of the 9/11 Museum for asking a museum visitor a question. We also found out that the museum's gift shop was selling 9/11 cheese plates (the "commemorative plates" are removed a week later).

Photograph by Scott Lynch/Gothamist

November 2014: Office tenants move into 1 World Trade Center. Many of them work for Conde Nast. Window washers are saved after a scary scaffolding mishap outside the 67th floor.

December 2014: The NY Times reports that the Calatrava-designed $4 billion transit hub is insanely over-budget and looks cheap.

Thank God they have a selfie stick (Scott Lynch / Gothamist)

May 2015: One World, the observatory atop 1 World Trade Center, opens to the public with breathtaking panoramas, perfect for the selfie-obsessed public.

Of note: The gift shop has $200 pullovers. Also, it's pretty crazy when lightning strikes the spire.

July 2015: It's revealed that Calatrava's bird winged oculus at the transit hub will in fact open: On each September 11, the wings will open for 102 minutes, which is the elapsed time from the first plane hitting the World Trade Center until the second tower collapsed.

Bjarke Ingels' Two World Trade Center design

Bjarke Ingels offers an intriguing design for Tower 2. News Corp and 21st Century Fox will be anchor tenants.

Also: Plans for an ambitious arts center shrink.

August 2015: The World Trade Center's slurry wall might be leaking.

The oculus, last week (World Trade Center Progress Facebook)

September 2015: Pope Francis will visit the 9/11 Memorial and Museum on September 25.