As of April 2015, the International Space Station (ISS) is the most expensive man-made object ever built. The ISS project has cost approximately $160 billion as of 2015, with the United States contributing more than $100 billion and Europe, Russia, Japan and Canada combining to pay the rest.

The seeds of the ISS project began in 1985 as a response to President Ronald Reagan’s 1984 State of the Union address, in which he said the U.S. would build a space station within a decade. For nearly ten years afterward, NASA spent $8.8 billion developing blueprints for a U.S.-only space station, but it was not put into production. In 1993, following the collapse of the Soviet Union, President Bill Clinton oversaw an agreement with Russia, Japan, Canada and a cooperative of several European nations to build and man the ISS.

In the first thirty years of the ISS project, NASA had a budget of $58.7 billion devoted to it. The agency spent an additional $54 billion sending space shuttles to the station for construction and maintenance. The ISS has had a crew on board since 2000, adding further costs to the total budget.

As of 2015, the cost of maintaining the ISS is estimated at $3 billion per year, prompting many to debate whether the project’s return on investment is worth its cost. Some argue that the cost is justified by potential research opportunities available in space, where the weightless environment makes possible projects that cannot be achieved on Earth. Others contend that the likelihood of such research producing results worth the high price is slim.