All the major sections of the Apollo spacecraft and launch vehicle, with the exception of the Grumman-built Lunar Module, were developed and built by companies that would later join to form 21st century Boeing. These companies had a common customer, NASA, which led the U.S. effort to put a man on the Moon and return him safely to Earth. North American assembled the command and service modules at its Downey plant, with astronauts dropping by to assist with component testing and cockpit design. A separate North American facility at Seal Beach was used to manufacture the second Saturn stage. In Canoga Park, North American's Rocketdyne division was working on the Saturn engines, and near Santa Monica, Douglas was manufacturing the third Saturn stage.