Per NASA press release:
Atlantis and its four astronauts left Earth for the final space shuttle mission, which will cap off an amazing 30-year program of exploration, which launched great observatories, built an International Space Station, and taught us more about how humans can live and work in space.
With the International Space Station flying 220 miles high and east of Christchurch, New Zealand, Atlantis left Launch Pad 39A at NASA's Kennedy Space Center in Florida at 11:29 a.m. EDT. There was a slight delay at T-31 seconds while retraction of the Gaseous Oxygen Vent Arm, or "Beanie Cap," was verified. Atlantis will dock with the space station on Sunday.