Though the MGM version of Hollywood's most famous evil witch would have been impossible without the L. Frank Baum model, Baum doesn't seem particularly fascinated with his witch's personality in THE WONDERFUL WIZARD OF OZ. Baum provides most of the important tropes-- the idea of the witch as a negative mother-figure (she makes Dorothy serve her for a period, in contrast to the movie), and the idea that Dorothy can vanquish her by a careless act of aggression, simply splashing her with a bucket of water. But the witch of Baum's book, though she is an important femme formidable (and covered in this essay), just doesn't have the magnificently nasty personality of the MGM film.
There's some irony to this, since one of the film's early scripts considered making the Witch of the West a glamorous figure, to be played by Gale Sondergaard. Fortunately a different vision prevailed, and the Witch became the incarnation of the wickedness of the archetypal Crone. This image is further reinforced by giving the Witch an identity in the real world outside the dream of Oz: a nasty old bitch who uses money the way the Witch uses her poppies and flying monkeys.
In contrast to Baum's rambling novel, the Witch is the only antagonist of the 1939 movie, so that Margaret Hamilton's delicious evil perfectly parallels the tremble-lipped innocence of Dorothy. The pervasiveness of the Witch's influence on pop culture is demonstrated by a statement made by Margaret Hamilton made when she made public appearances and was asked to duplicate her character's distinctive cackle. In essence she said, "They like to hear it-- and yet they also don't like to hear it." Such ambivalence captures the fundamental appeal behind every great villain, male or female.