The eccentric businessman, with usual flair, sported a black jacket and waves of hair flying as he inaugurated the building by breaking a champagne bottle against a hanger building, while rappelling down the side of it.
"Spaceport America," as the site is called, will serve "as the operating hub for Virgin Galactic and is expected to house up to two WhiteKnightTwos and five SpaceShipTwos, in addition to all of Virgin?s astronaut preparation facilities and mission control," said the company in a statement to the press.
About 150 people already booked for travel on the first flights to orbit attended the event, said the company.
Also attending were head of Virgin Galactic George Whitesides, commercial director Stephen Attenborough, and famed US astronaut -- and second human being to step on the moon -- Buzz Aldrin.
Branson last month said he hoped to launch a vessel into space within the next 12 months, which he said would kick off an era of commercial space travel.