DENDRAL is widely regarded as the first expert system

DENDRAL was a research program begun at Stanford around 1965, led by Edward Feigenbaum, Joshua Lederberg, and Bruce Buchanan, to take the readings from a mass spectrometer and work out which organic compound produced them. Where the earlier Logic Theorist had searched for proofs in pure logic, DENDRAL was the first system to capture the specialized know-how of human experts in a real scientific field and put it to practical work, and it is widely called the first expert system. Its lesson, that an AI’s power comes less from clever search than from the expert knowledge built into it, founded the discipline Feigenbaum called knowledge engineering.