Year of Decision 1846 Author:Bernard De Voto "In the first volume of the trilogy, Devoto made 1846 the 'year of the decision.' The reason was that it was in 1846 that America began a war with Mexico that would lead to the annexation of New Mexico, Arizona, and California; and that America settled a long-smoldering dispute with Great Britain and became sovereign in Oregon, thus beginning th... more »e process of making the Southwest and West Coast into a part of the American Republic. It was also a peak year in the emigration across the plains and mountains." --Stephen E. Ambrose, from the Introduction« less