"A true poem," Walt Whitman proclaimed in 1852, "is the daily newspaper"--and American culture was never the same again. Like a blast of cold air in a stuffy drawing room, Whitman's campaign to give artistic representation to gritty reality shocked the genteel artistic elite of the 1850s; but the brassy poet's efforts helped generate a revolution in American life and thought. Four decades later, Willa Cather could declare that the "public demands...