 American expansionists favored setting the border at the Rio Grande, but Spain, intent on protecting its colony of Mexico from American encroachment, insisted on setting the boundary at the Sabine River.At Monroe's direction, Adams agreed to the Sabine River boundary, but he insisted that Spain cede its claims on Oregon Country.Adams was deeply interested in establishing American control over the Oregon Country, partly because he believed that control of that region would spur trade with Asia.