"One of the few really helpful words I ever heard from an older writer," Willa Cather declared in 1922, "I had from Sarah Orne Jewett when she said to me: 'Of course, one day you will write about your own country. In the meantime, get all you can. One must know the world so well before one can know the parish.'" Although Cather's first novel about her own country, O Pioneers!, did not appear un…