IBM (1975)
IBM 5100, introduced in September 1975, was IBM's first portable computer.
The 5100 was just one of several portable computers IBM made before the Personal Computer (PC).
The 5100 model was followed by the 5110, the 5120, the Datamaster, and then finally the 5150 PC.
From http://www.blinkenlights.com/pc.shtml