Webb has over 1200 skilled scientists, engineers and technicians from 14 countries (and more than 27 US states) building it. (It is a joint NASA/ESA/CSA mission.) Assembly and testing of the mirror and instruments occurred at NASA Goddard.
Some of the James Webb Space Telescope team are shown here in front of the
Webb full-scale model at the Goddard Space Flight Center in Greenbelt, Maryland.