Pasadena's Jet Propulsion Laboratory is a control center for robotic space exploration, yes, but its origins are older than that. It was started in
the 30's as an informal testbed for Caltech rocketeers, but on November 20, 1943, the Jet Propulsion Laboratory was officially conceived to design a rocket that would compete with Axis Germany's V-2 Rocket.
Their first rocket, the Private A, flew December 1944, and achieved a range of 11 miles. Their next rocket, the WAC Corporal made history when in 1949, one was launched from the nose of a V2 rocket, achieving an altitude of 244 miles, becoming the first United States rocket to enter outer space.
Starting with Explorer 1 (our first satellite) in 1958, JPL changed its focus from the rockets to what sits on top of them. JPL's Surveyor missions gathered the data necessary for the success of the Apollo missions. Thusly, JPL has pioneered many now common techniques for space exploration, for instance, Mariner 10, launched in 1973, was the first probe to use gravity assist slingshotting to boost its speed.
JPL engineers designed and built the twin Voyager probes which did the first thorough mapping of Mars, and proceeded then to spiral out of our solar system, discovering such interesting things on the way as active volcanoes on Jupiter's moon, Io. Surprisingly, the Voyager mission is still ongoing; both spacecraft are now leaving our neighborhood entirely, and still sending back worthwhile data.
JPL engineers fitted those extraterrestrial eyeglasses onto the Hubble Space Telescope that changed it from myopic money drain to fascinating source of wonderful images. They designed and built the Mars Pathfinder.
JPL scientists aren't all work, though, mechanical engineer Lonnie Johnson designed the Super Soaker, which has earned him not only $500 million in profits, but also a world-famous invention. The dress code is notoriously relaxed; there's a classic picture of an audience at a missile test, five crisp Army and Air Force men, and one shirtless JPL man.
JPL's full history is a long and detailed story, which I've highlighted here, but if you want to read more, the full story (as well as my source) is here: http://www.jpl.nasa.gov/about_JPL/, and more specifically, http://www.jpl.nasa.gov/about_JPL/jpl101.pdf