[acqq]

http://en.wikipedia.org/wiki/Programmed_Data_Processor

   PDP-1  18 bit
   PDP-2  24 bit
   PDP-3  36 bit
   PDP-4  18 bit
   PDP-5  12 bit
   PDP-6  36 bit
   PDP-7  18 bit

http://en.wikipedia.org/wiki/PDP-7

"In 1969, Ken Thompson wrote the first UNIX system in assembly language on a PDP-7, then named Unics as a pun on Multics"

CDC "super" computers also had 60-bit words.

Moreover, the original ASCII standard had the 7-bit characters, the improvement over even less bits used for characters before that (6 bits == 2 octal digits). 8-bit bytes weren't something you could expect except when buying IBM (which had EBCDIC, not ASCII).