The space shuttle Endeavour has landed at Kennedy Space Center in Florida, following its latest visit to the International Space Station (ISS).
The two-week mission saw the virtual completion of the ISS.
The six-member crew of Endeavour installed the Tranquility Node, a spacious addition that includes the "cupola" observation deck.
The commissioning of Tranquility marks the last major component on the US side of the space station.
The $100bn project, involving five space agencies, is nearly completed after more than a decade of construction 340km (210 miles) above the Earth.
As the Endeavour crew parted with colleagues on the ISS on Friday, space station commander Jeffrey Williams congratulated the shuttle astronauts on their successes in installing Tranquility.
"We are really going to enjoy the view. I wish you guys could stay a little longer to partake in that view," he said.
A further four shuttle missions will occur over the coming seven months, each of which will bring equipment and supplies to the station.
The space shuttle fleet will then be retired.
One of the last missions will launch a mini-module for the Russians. Another will take up a big science experiment called the Alpha Magnetic Spectrometer.
The final orbiter missions will also be packed with spares that are too big to be carried by the existing fleet of robotic cargo ships.
On retirement of the shuttle fleet, the job of launching astronauts to the station will become the sole responsibility of Russian Soyuz vehicles until the Americans can develop a new crew carrier of their own.