BAIKONUR, Kazakhstan (AP) _ Born in Cold War secrecy and the scene of Soviet space triumph and tragedy, the Baikonur cosmodrome marked its 50th anniversary Thursday, hailed by the presidents of Russia and Kazakhstan as a technological workhorse on the wind-swept steppes of Central Asia.

Baikonur launched the first satellite and the first man into space, and is now home to the Soyuz rockets that service the international space station, shuttling crucial deliveries, along with Russian cosmonauts and American and European astronauts.

At a ceremony celebrating the cosmodrome's construction in 1955, a decade after the end of World War II, Russian President Vladimir Putin hailed it as ''a heroic feat ... of the people who had just gone through a devastating war.''

''Today, Baikonur is rightly considered the world's leading cosmodrome, and it's good that its unique potential is being actively engaged and is developing consistently,'' Putin said, accompanied by Kazakhstan President Nursultan Nazarbayev. ''It makes a key contribution to the international space station.''

Initially designed as a testing ground for a top-secret Soviet ballistic missile program, Baikonur was a key site in Moscow's space race with the United States in the 1950s and 1960s, and saw many historic firsts in exploration.

Sputnik, the first satellite to orbit the Earth, blasted off from here in 1957, and cosmonaut Yuri Gagarin, the first man in space, was launched from Baikonur in 1961 _ 23 days before the United States sent aloft its first astronaut, Alan Shepard.

Baikonur also sent the first woman into space, Valentina Tereshkova, in 1963, and was used for missions that built and maintained the space station Mir in the 1980s and 1990s.

For all the success at Baikonur, there was also disaster: A missile exploded on a launchpad on Oct. 24, 1960, killing 165 workers. The accident was shrouded in secrecy for 30 years.

After the 1991 Soviet collapse, Kazakhstan inherited the cosmodrome and now leases it to Russia, which uses it as its sole launch site for manned space missions.

In the past two years, Baikonur has been the only gateway to the international space station since the U.S. space shuttle fleet was grounded after Columbia disintegrated during its return to Earth, killing all seven astronauts aboard.

The cosmodrome extends for 50 miles from north to south, and for 80 miles east to west. It has dozens of launch pads and five tracking-control centers, nine tracking stations, and a 930-mile missile test range.

During their visit, Putin and Nazarbayev toured a plant where Proton rockets and satellites are assembled. They later met with veterans of space exploration.

They also laid the foundation stone of a new joint Russian-Kazakh launch complex, Baiterek, for the more environmentally friendly Angara vehicle. The Angara is meant to be an alternative to Russian boosters now in use, some of which use poisonous fuel and litter the countryside with the debris of burned-out rocket stages.

The $400 million complex is expected to be completed in 2008-2009.

The Baiterek project is seen as the result of Kazakhstan's long campaign to minimize pollution from rocket launches from their territory and also a breakthrough in the oil-rich nation's ambitious plans to become Russia's partner in space exploration.

Russia pays $115 million annually for the use of Baikonur under a deal effective through 2050. The cash-strapped Russian space agency has abandoned many programs since the collapse of the Soviet Union, leaving many Baikonur facilities to rust and crumble.