In the Fall of 1998 Nintendo Power held a contest to “Win Mew for your Pokémon collection!” 151 winners of this contest would be given the chance to mail their cartridge into the Nintendo Power Headquarters and receive it back with a brand-new mew on their game save. Contest winners were notified by mail by 2/28/1999 that they had won the contest, making this the earliest known Mew distribution in the west.
More can be read on the original thread.
THIS POKEMON WILL NOT BE LEGAL WITH ANY VIRTUAL CONSOLE RELEASE
(AND BY EXTENSION, CANNOT BE SENT TO GEN 7 AND ONWARD).
@Gridelin, @suloku and /u/Th4tGuyUKn0