The US space agency sent its last shuttle, Atlantis, out to the launch pad at Kennedy Space Center so it can prepare for the final launch of the American shuttle program in July.
The shuttle began its trek at 8:00 pm (0000 GMT) on Tuesday.
The familiar ritual of rolling a massive shuttle from the Vehicle Assembly Building on a slow journey along a stone-covered crawlerway was a powerful symbol to the thousands of NASA employees who gathered to watch it go.
Atlantis's mission, STS-135, is set to launch on July 8 toward the International Space Station and will be the last journey by a US shuttle before the three-decade program officially draws to a close.
The end of the US shuttle program leaves Russia as the only nation capable of toting astronauts into space until a replacement US vehicle can be built, likely no earlier than 2015.
Explore further: Successful engine test enables SpaceX Falcon 9 soar to space station in Jan. 2015