"Most of the books published during the five-year period leading up to, during, and after the invasion of Mexico were war-mongering tracts. Euro-American settlers were nearly all literate, and this was the period of the foundational "American literature," with writers James Fenimore Cooper, Walt Whitman, Edgar Allan Poe, John Greenleaf Whittier, Henry Wadsworth Longfellow, James Russell Lowell, Ralph Waldo Emerson, Henry David Thoreau, Nathaniel Hawthorne, and Herman Melville all active-each of whom remains read, revered, and studied in the twenty-first century, as national and nationalist writers, not as colonialists. Although some of the writers, like Melville and Longfellow, paid little attention to the war, most of the others either fiercely supported it or opposed it...Opposition to the Mexican War came from writers who were active abolitionists such as Thoreau, Whittier, and Lowell. They believed the war was a plot of southern slave owners to extend slavery, punishing Mexico for having outlawed slavery when it became independent from Spain."