(CNN)Here's some background information about the rebuilding of Ground Zero in lower Manhattan and the memorial to the victims of the September 11th attacks.
September 11th Memorial:
The memorial honors those killed on September 11, 2001 in all locations of the attack, as well as those killed on February 26, 1993, when terrorists set off a truck bomb in the basement of the World Trade Center.
April 28, 2003 - The World Trade Center Site Memorial Competition launches.
June 2003 - The Memorial Competition submission period closes. 13,683 people registered for the competition. 5,201 submissions are received from 63 nations.
November 19, 2003 - Eight prospective plans chosen from the submissions for a World Trade Center memorial are displayed for the public in the World Financial Center in New York.
January 6, 2004 - The Lower Manhattan Development Corporation announces its choice of "Reflecting Absence" by Israeli-born architect Michael Arad.
January 14, 2004 - Plans for the redesigned World Trade Center Memorial go public when the architect unveils his changes to "Reflecting Absence." The new plans include more greenery and park plazas around the reflecting pools that will go at the base of where the twin towers once stood and an underground museum.
September 10, 2005 - Supporters of the Take Back the Memorial campaign rally to protest the inclusion of an International Freedom Center (IFC) in New York's plans for the World Trade Center memorial.
September 28, 2005 - In a written statement, Governor George Pataki announces that plans for the International Freedom Center adjacent to the planned memorial at the World Trade Center site have been abandoned.
July 12, 2011 - More than 42,000 passes to the memorial are reserved in the first 24 hours they are made available.
September 11, 2011 - 10th anniversary of the 9/11 attacks and dedication date for the 9/11 Memorial.
September 12, 2011 - The memorial opens to the public.
2012 - A dispute between the Port of Authority of New York and New Jersey delays construction of the 9/11 museum planned for the Memorial site. The museum was originally supposed to open on the 11th anniversary of 9/11.
September 10, 2012 - The budgetary dispute delaying the opening of the museum is resolved when all parties enter into a "memorandum of understanding," an agreement that allows them to restart construction.
May 15, 2014 - The National September 11 Memorial & Museum opens its doors for the 9/11 community -- survivors, families, rescuers. Within it are 12,500 objects, 1,995 oral histories and 580 hours of film and video.
May 21, 2014 - The National September 11 Memorial Museum opens to the public.
December 9, 2014 - Prince William and his wife, Kate bring a bouquet of flowers to the 9/11 memorial and place it near one of the twin reflecting pools during a royal visit.
Redevelopment of Lower Manhattan:
Fall 2001 - New York Governor George Pataki and New York City Mayor Rudy Giuliani create the Lower Manhattan Development Corporation (LMDC). The mission of the LMDC is to "help plan and coordinate the rebuilding and revitalization of Lower Manhattan," after the attacks of September 11, 2001.
The LMDC also administers the World Trade Center Site Memorial Competition, a separate process from that of rebuilding the World Trade Center area.
A 15-member board of directors governs the LMDC. The governor of New York and the mayor of New York City each appoint half of the members. The LMDC is also assisted by nine advisory councils.
According to an audit conducted by the Port Authority of New York and New Jersey, the rebuilding cost has grown from approximately $11 billion in 2008 to the current estimate of approximately $14.8 billion.
August 12, 2002 - FEMA and the Federal Transit Administration announces $4.55 billion in federal aid for transportation improvements in Lower Manhattan.
September 26, 2002 - Six new design teams are hired out of 407 submissions to create land use plans for the 16-acre site.
December 18, 2002 - An exhibit of nine new WTC designs opens in the World Financial Center Winter Garden.
February 27, 2003 - Daniel Libeskind's "Memory Foundations" is selected as the new design for the World Trade Center site.
September 17, 2003 - The LMDC releases a revised Master Plan for the World Trade Center Site.
November 23 2003 - PATH train service is restored, linking Lower Manhattan and New Jersey. Trains operate out of a temporary station in the WTC area.
December 19, 2003 - Plans for the Freedom Tower to be built at Ground Zero are revealed.
January 22, 2004 - Architect Santiago Calatrava unveils his plans for the WTC transportation hub.
July 4, 2004 - Construction at the Freedom Tower begins. A 20 ton slab of granite, inscribed "the enduring spirit of freedom," is laid as the cornerstone of one of the new skyscrapers that will stand on the site.
May 4, 2005 - Governor Pataki calls for a redesign in the plans for the new tower for safety reasons.
June 29, 2005 - New York officials release the latest design for the signature building at the World Trade Center site after revising it to make the tower more secure.
September 6, 2005 - Architect Santiago Calatrava and public officials dedicate the first steel rail for the future transportation station to be built at the World Trade Center site.
December 15, 2005 - Architect Lord Norman Foster agrees to design the next major building planned for the World Trade Center site. Foster will design a 65-story tower for the northeast corner of the 16-acre site that real estate developer Larry Silverstein said will be completed by 2011.
April 26, 2006 - The Port Authority of New York and New Jersey and developer Larry Silverstein reach an agreement about the financing of Freedom Tower, resolving problems that had delayed construction at the WTC site.
April 27, 2006 - The formal groundbreaking of Freedom Tower takes place.
May 17, 2006 - Governor Pataki appoints Kevin M. Rampe chairman of the Lower Manhattan Development Corporation, to replace John Whitehead.
March 26, 2009 - The Port Authority of New York and New Jersey announces dropping the name "Freedom Tower," and that the first commercial lease in the building has been signed. Upon completion, the building will be named One World Trade Center.
July 2009 - Muslim investors purchase the property at 49-51 Park Place, two blocks north of the former World Trade Center.
May 7, 2010 - The Community Board of Lower Manhattan votes unanimously in favor of the Cordoba House Project, which includes plans for a 15-story community center, mosque, performing arts center, gym, swimming pool and other public areas.
July 2010 - The Cordoba House Project is renamed Park51.
Summer 2010 - Protesters demonstrate against construction of the Islamic community center and mosque near Ground Zero.
August 3, 2010 - Plans for the Islamic center continue as New York City's Landmarks Preservation Commission denies landmark status to 45-47 Park Place, a nearby building.
August 3, 2010 - New York Mayor Michael Bloomberg speaks in favor of the center, that blocking the center would be an affront to religious freedom.
August 13, 2010 - President Barack Obama expresses his support for Park51, citing freedom of religion.
September 21, 2011 - A small section of the planned Park51 center opens with the debut of NYChildren, a photography exhibit showcasing the portraits of New York City children originating from over 160 countries.
May 10, 2013 - Construction workers bolt the last pieces of a 408-foot spire into place atop One World Trade Center, bringing the building to a height of 1,776 feet. This height references the year the United States declared its independence. It also makes the building the tallest in the Western Hemisphere and the third tallest in the world.
April 7, 2014 - The owner of Park51, Sharif El-Gamal files an application to demolish the community center, as well as a neighboring property. A month later, he seeks a permit to redevelop the site, possibly as a museum and condominium complex.
May 29, 2015 - The observatory opens in the top three floors of One World Trade Center.