Jet Propulsion Laboratory, founded in 1936 by California Institute of Technology researchers in La Cañada Flintridge, grew from hazardous Arroyo Seco rocket tests by a small Caltech-led group into NASA’s principal center for robotic missions beyond Earth orbit. After gaining U.S. Army backing, it developed jet-assisted takeoff rockets and early ballistic missiles before helping launch Explorer 1 in 1958, the first U.S. satellite. Transferred to NASA later that year, JPL went on to lead major lunar, planetary, Earth-orbiting, and astronomy missions, including Voyager, Galileo, Cassini-Huygens, Pathfinder, and prominent Mars rovers, while also operating the Deep Space Network and tracking near-Earth asteroids.