WTC 1 is topped off at 110 floors in 1970; its first tenants move in. Building is completed in 1972. WTC 1 becomes the world's tallest building at 417 meters, overtaking New York's Empire State Building. It loses the top spot to Chicago's 443-meter Sears Tower in 1974. A 110-meter telecom antenna is installed on WTC 1’s roof in 1979, giving it a new height of 527 meters.

The North Tower is the first to be struck by a hijacked plane on 9/11. It is the second tower to collapse.

A Memorial Pool encompassing the North Tower's footprint is due to be opened on September 11, 2011.

WTC 2 is topped off at 110 floors in 1971, first tenants move in. It becomes the world's 2nd tallest building at 415 meters. Construction is completed in 1973. WTC 2's unique features include its 107th and 110th floor observation decks, which become popular tourist attractions.

The South Tower is the second to be struck by a hijacked plane on 9/11. It is the first tower to collapse.

A Memorial Pool encompassing the South Tower's footprint is due be opened on September 11, 2011.

WTC 3 opens in 1981. The 22-story, 800-room Vista International Hotel becomes the first major name-branded hotel in Lower Manhattan. A bomb explodes in a WTC underground parking lot on February 26, 1993, killing six people and damaging areas under the hotel. It re-opens in November 1994 after repairs. Marriott International takes over management of the hotel in 1995 and renames it Marriott World Trade Center.

After hijacked planes hit the Twin Towers, Marriott staff evacuate of hundreds of guests. Hundreds of workers flee the North Tower through the hotel's lobby. Collapse of the Twin Towers levels almost the entire hotel. Its remains are demolished as part of the Ground Zero cleanup. Two Marriott employees and at least 41 firefighters die. Eleven registered hotel guests are unaccounted for.

The site of the former hotel is now part of the 9/11 Memorial Plaza.

WTC 4, a nine-story office building, opens to its first tenants in 1977. Major occupants include Deutsche Bank and the New York Board of Trade.

Most of WTC 4 is crushed by the collapse of the South Tower. Its remains are demolished as part of the Ground Zero cleanup.

A new 4 WTC is under construction on part of the site. (see right) Silverstein Properties says it will be completed in 2013. A new 3 WTC is under construction on another part of the site. (see left) Silverstein Properties says it will be completed in 2015.

The 72-story 4 WTC will be the 4th tallest in the WTC complex. (see right) It will house the new headquarters of the Port Authority of New York & New Jersey. The 80-story 3 WTC will be the 3rd largest in the WTC complex. (see left)

WTC 5, a nine-story office building, opens to its first tenants in 1972. Major occupants include Credit Suisse First Boston and Morgan Stanley.

WTC 5 is gutted by fire and debris after the collapse of the nearby Twin Towers. It is demolished as part of the Ground Zero cleanup.

A new 2 WTC is under construction on part of the site. Silverstein Properties says it is "expected" to be completed in 2016. (see top) A new WTC Transportation HUB is under construction on another part of the site. The Port Authority of New York & New Jersey says it will be completed in late 2014. (see bottom)

The 88-story 2 WTC will be the 2nd tallest building in the WTC complex and in New York, with a height of 411 meters. Transportation HUB designer Santiago Calatrava says the station's roof is intended to resemble a dove released from the hands of a child.

WTC 6, an eight-story building known as U.S. Customs House, opens in 1974. Tenants are primarily federal government agencies, including the Departments of Agriculture, Commerce and Labor and the Bureau of Alcohol, Tobacco & Firearms.

Collapse of the North Tower on 9/11 leaves deep craters in the building. It is demolished as part of the Ground Zero cleanup.

A new 1 WTC is under construction on part of the site. The Port Authority-owned 104-story building will be completed at the end of 2013. 1 WTC's top floors will contain an observation deck, restaurants and television broadcast facilities. 1 WTC will be the tallest office tower in the U.S., with a height of 1,776 feet (representing the year of U.S. independence) or 542 meters.

A new Performing Arts Center, designed by architect Frank Gehry and partners, is planned to be built next to 1 WTC. Its design includes a 1,000-seat theater, rehearsal spaces, classrooms and a public cafe. New York City Hall says foundation work for the Center will continue until 2014. It is expected to open in 2019.

WTC 7, a 47-story office building, opens in 1987. Investment bank Salomon Smith Barney is the main tenant. Other tenants include American Express Bank International, ITT Hartford Insurance Group, the Securities and Exchange Commission and Standard Chartered Bank.

Occupants evacuate WTC 7 on the morning of 9/11. As the North Tower collapses, debris hits WTC 7's southern facade, triggering a major fire. Debris from the Twin Towers damages a water main that supplies WTC 7's sprinkler system, depriving it of water to douse the flames. The fire burns uncontrolled for hours until WTC 7 collapses at 5:20 pm on 9/11.

Construction of a new WTC 7 starts in 2002. The 52-story tower is completed in 2006. Major tenants include Moody's, WestLB, New York Academy of Sciences, Arnell Group, Ameriprise Financial, BMI, Silverstein Properties and Mansueto Ventures.

St. Nicholas Greek Orthodox Church is founded in 1916 by Greek immigrants who settle in Lower Manhattan after arriving at nearby Ellis Island. Church founders, many of them shipping workers, dedicate the four-story building, constructed around 1832, to St. Nicholas, the patron saint of sailors.

St. Nicholas is flattened by the collapse of the South Tower. No one is inside the church. A few religious artifacts are recovered, including a small bell and a paper icon. After cleaning up the site and reaching agreement with its owners, authorities hope to convert it into an underground vehicle screening center for cars, trucks and buses entering the new WTC complex.

In 2008, the Port Authority of New York & New Jersey says authorities agree to give the church money and land to rebuild St. Nicholas in a future park near the original site. The Greek Orthodox Archdiocese of America agrees to hand over land rights to allow excavations to begin. Negotiations to finalize the deal break down in 2009. The Port Authority continues excavation work at the site. The Greek church sues the Port Authority in a federal court in February 2011, accusing it of reneging on the agreement.

A 40-story office building and plaza at 130 Liberty Street opens in 1974 as Bankers Trust Plaza. It is renamed the Deutsche Bank Building after the German bank buys Bankers Trust in 1999. The Deutsche Bank Building is almost entirely evacuated when debris from the South Tower leaves a huge gash in its northern facade. A security guard is killed in the basement.

The building is contaminated with toxic dust from the WTC site and mold caused by rain that blows in through broken windows. Deutsche Bank declares it unfit for habitation in 2002 and begins a legal battle with insurers to settle the loss. Lower Manhattan Development Corporation (LMDC) buys the building in 2004 and begins demolition in 2007. An accidental fire erupts in August 2007, killing two firefighters. Demolition resumes in November 2009 and reaches the basement in February 2011.

LMDC begins excavating the site down to bedrock to build a Vehicle Security Center (VSC) for the new WTC complex. After the VSC is completed in late 2013, the northern part of the site will be developed into Liberty Park, extending to a nearby area that housed St. Nicholas Greek Orthodox Church. Most of the site is reserved for construction of a Port Authority-owned 5 WTC tower that may be used for offices, apartments or a hotel.

A 16-story office building at 30 West Broadway opens in 1959. Its owner, Miles Fiterman, donates the building to the City University of New York (CUNY), which makes it part of CUNY's Borough of Manhattan Community College in 1993. CUNY renames the building Fiterman Hall in honor of the businessman’s gift.

Fiterman Hall is evacuated on 9/11, six weeks before ongoing renovations are due to be completed. Debris from the collapse of WTC 7 hits the southern facade, sparking a fire and damaging the building. Toxic dust and mold also infest the structure. CUNY decides Fiterman Hall should be torn down and rebuilt. It reaches an insurance settlement for the loss in 2004 after lengthy negotiations.

A deal to rebuild Fiterman Hall is reached in November 2008, using funds from New York city and state governments, the Lower Manhattan Development Corporation and CUNY's insurance settlement. Foundation work for the new Fiterman Hall begins in 2009. It is due to open in the second half of 2012.

The World Trade Center towers and plaza are dedicated in a ceremony on April 4, 1973. The plaza's centerpiece is a bronze sculpture known as The Sphere, by German sculptor Fritz Koenig. The Port Authority of New York & New Jersey renames the plaza in honor of its former executive director, Austin J. Tobin, after his death in 1978.

The collapse of the Twin Towers destroys the plaza, but The Sphere suffers only slight damage. It is moved temporarily to nearby Battery Park in 2002 and put on display as a tribute to the victims of the attacks.

The site of the former WTC plaza is now part of the 9/11 Memorial Plaza and contains a new structure: a pavilion for a large, underground 9/11 Memorial museum scheduled for opening in September 2012.