The Apollo Guidance Computer was the first recognizably modern embedded system. It was developed by Charles Draper and the MIT Instrumentation Laboratory. Each flight to the moon had two of these computers. They ran the inertial guidance systems of both the command module and LEM.
The Apollo flight computer was the first to use integrated circuits. The computer consisted of roughly a thousand identical integrated circuits, NAND gates. They were interconnected by a technique called wire wrap, in which the circuits are pushed into sockets, the sockets have square posts, and wire is wrapped around the posts. The edges of the posts bite the wire with tons of pressure per square inch, causing gas-tight connections that are more reliable than soldered PC boards. The wiring was then embedded in cast epoxy plastic.