The GRiD Compass 1100, introduced by Grid Systems Corporation in 1982, was probably the first commercial computer created in a "clamshell" laptop format, and one of the first truly portable machines.
The 1100 included a magnesium clamshell case with a screen that folded flat over the keyboard, a switching power supply, electro-luminescent display, non-volatile bubble memory, and a built-in modem.