"Bob and Doug, we here at SpaceX are honored to have been part of the ushering in of this new era of human spaceflight", SpaceX engineer Anna Menon said.
Behnken, in turn, congratulated the teams at SpaceX and NASA.
"Their incredible efforts over the last several years to make this possible can not be overstated", he said of the SpaceX employees. Just before liftoff, Hurley said, "SpaceX, we're go for launch".
Behnken joked about Hurley's brief manual piloting experience.
It will also be the first time a private company launched men into space.
NASA astronauts Bob Behnken and Doug Hurley have successfully reached orbit aboard a SpaceX spacecraft, the culmination of the better part of a decade of work. The company has been testing prototypes of its next-generation rocket and habitat, Starship, in Texas. "It's been 18 years working towards this goal, so it's hard to believe that it's happened".
The space agency also estimated 1.7 million people were watching the launch preparations online during the afternoon.
No issues with the spacecraft have been reported - described by a SpaceX commentator as "pretty boring for the astronauts, but that's what we wanted. We haven't done this really since 2011, so this is a unique moment in time", Bridenstine said.
SpaceX and NASA monitored the weather not just at Kennedy Space Center, where rain, thick clouds and the chance of lightning threatened another postponement, but all the way up the Eastern Seaboard and across the North Atlantic to Ireland.
The capsule autonomously attached itself to the space station in a "soft capture" at 7:16 a.m. The Crew Dragon is certified for a stay of up to four months in space, and the return journey will likely be ahead of that time.
The International Space Station was only accessible to NASA astronauts through the purchase of seats on Russian capsules launched from Kazakhstan- but that has all changed as of today.
Behnken is scheduled to make several spacewalks with Cassidy, as Hurley monitors and controls instruments inside the station. Contrary to the usual NASA procedure, SpaceX fueled up the Falcon 9 after the two astronauts had already boarded the Dragon.
It would also have been the first time in almost a decade that the United States launched astronauts into orbit from U.S. soil. Boeing's spaceship, the Starliner capsule, is not expected to fly astronauts until early 2021.