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It's a chip-fabrication plant now, but when it was opened on 23 June, 1958 — by a signal picked up from America's first orbiting satellite — it was a development lab and home to new hire Jack Kilby. And no sooner had everyone moved in, than they went on their two-week vacation. All except Jack, who was too new to have earned any. Desperate to avoid having to wire up thousands of tiny connections for transistorised modules when everyone came back, he used his time in the empty lab to come up with the idea of making all the components in a module out of a single piece of semiconductor, thus creating the idea of the integrated circuit. Forty-two years later, that got him the Nobel Prize.
Real-life visiting potential: 1/10. The local dignitaries have erected a plaque outside the plant, but the place itself is not open for visitors. And North Dallas is a long way to go to see a plaque.