Julia Morgan's most famous building is Hearst Castle at San Simeon, but in many ways it is not representative of her best work (though the terraces, gardens and pools are fabulous). To me, the thing that is most striking about Morgan's designs is the skill with which they are fit to the needs and personalities of the clients for whom they were built (which may be why Hearst Castle is less interesting to me -- consider who the client was). Though her designs manage to be both functional and beautiful across a wide range of styles and programs, they are also consistently humane.
Here are some links:
Great Buildings Online biography