How The Original King Kong Movie Was Made

Great article on the
making of the original.
Kong was actually an 18 inch high, poseable model, covered with rabbit hair, that was filmed one frame at a time by stop-motion photography artist Willis O'Brien and his crew (Despite some stories no man in an ape suit was ever employed) on miniature sets of the jungle and New York City. While the stop-motion technique had been around for over a decade, O'Brien and other special effect technicians were able to combine it with other techniques, such as rear projection and miniature projection, to place the actors in the shots with Kong in a way not seen before.
(via
Make:Blog)