Georgia Totto O'Keeffe was a major figure in American art from the 1920s. She is mainly known for paintings of flowers, rocks, shells, animal bones, and landscapes in which she "synthesized abstraction and representation". What this means, I guess, is that she took real subject matter and transformed it into abstract images. She is also credited with bringing an American style of art to Europe during a period when most influence came from Europe to America - so I like her, at least, for that.
The two paintings above are examples of her work. Not sure if they are among her most famous, but I recognize them as her work. Kind of weird, huh?