ABSTRACT
Many American historians in the twentieth century, especially those who wrote during two decades following World War II, explained the expansion of the United States during the 1840s in terms of "manifest destiny" or "mission," concepts that the Jacksonian Democrats themselves had occasionally employed to sanction their policies. During the Senate debates on the war and issue of territorial indemnity, Calhoun insisted that the color line be drawn at the Rio Grande River and that the United States not extend its jurisdiction south of it. The debates over Indian policy, the Oregon controversy, and Mexican War generated considerable speculation concerning the bleak prospects for Native Americans and mixed-blood Mexicans on the continent, but the protracted dispute over the Wilmot Proviso reignited the powerful fears about the country's largest and most menacing minority—the blacks. Democrats agreed on the desirability of obtaining vast territorial cessions, but they disagreed on where, when, and how the color line should be drawn west of the Mississippi.
