Daniel Walker Howe, a Pulitzer Prize-winning historian known for his acclaimed book "What Hath God Wrought," has died at age 88. The book, published in 2008, chronicled the significant technological and social transformations in the United States between 1815 and 1848. Howe, a professor emeritus at UCLA, documented the nation's westward expansion, the rise of political parties, and the growing divisions over slavery.