As President, James Monroe presided quietly during a period known as "the era of good feeling." The frontier was moving rapidly westward, and small cities sprang up west of the Mississippi River. Monroe sent General Andrew Jackson on a military expedition into Florida which resulted in the purchase of Florida from Spain. Rapidly extending frontiers soon caused Americans to consider whether slavery should be permitted in the new territories. The Missouri Compromise "settled" this problem for nearly 30 years by setting definite limits to the extension of slavery in land lying within the Louisiana Purchase area.