The orbital assembly of the ISS began with the launch of the U.S.-funded and Russian-built Zarya module from Kazakhstan on November 20, 1998. Zarya, which means 'dawn,' was the ISS's first component.
Two weeks later on December 4, 1998, the U.S. shuttle Endeavour delivered the second Unity module, which docked with Zarya two days later. Both units were connected in July 2000 with the Zvezda module, which had been delivered earlier in the year by a Russian Proton carrier rocket.
The ISS has continued to expand and develop, and in October, 2007 saw the addition of the Italian-made Harmony Node 2 module.
The project currently involves NASA, Russia's Federal Space Agency, the Canadian Space Agency, Japan Aerospace Exploration Agency (JAXA), and 11 members of the European Space Agency (ESA). The agreement to build the ISS was signed in Washington on January 29, 1998.
"Sixty years ago, people in Europe were fighting one another," Alan Thirkettle, ISS Program Manager, European Space Agency, said as quoted on NASA's website.
"Now, they're working together, working on spacecraft and space stations. Two decades ago, the Cold War was still going on and here we are working with the Russians, the Americans, the Japanese, the Europeans, everyone working together. It seems a far better thing to be doing than what we were doing 60 years ago," Thirkettle said.
A total of 167 people representing 15 countries have visited the ISS, including 15 permanent and 13 visiting expeditions since the first crew arrived in 2000.
Through 114 spacewalks and unparalleled robotic construction in space, the station's truss structure has grown to 291 feet (89 meters) long. Its solar arrays now span to 28,800 square feet (2,675 sq meters), large enough to cover six basketball courts, according to NASA.
The ISS's 18th expedition - U.S. astronauts Mike Fincke and Greg Chamitoff, and Russia's Yury Lonchakov - currently playing host to visiting Endeavour shuttle astronauts, will not celebrate the anniversary on Thursday, Russian Mission Control said.
"The ISS's work schedule is very busy on Thursday. The crew have to make another spacewalk under a U.S. program, carry out regular maintenance of the Elektron oxygen generators, and do a lot of other things," spokesman Valery Lyndin said.
In addition to the various scientific experiments carried out on board the ISS, the research facility has also received a number of space tourists.
