Madison, Monroe, and Adams
Under Jefferson's successor, James Madison, the continued depredations of American shipping, combined with the clamor of American “war hawks” who coveted Canada and Florida, led to the War of 1812, which was, however, opposed in New England. The Treaty of Ghent settled no specific issues of the war, but did confirm the independent standing of the young republic. Politically, the period that followed was the so-called era of good feeling. The Federalists had disintegrated under the impact of the country's westward expansion and its new interests and ideals. Democrats of all sections had by now adopted a Federalist approach to national development and were temporarily in agreement on a nationalist, expansionist economic policy. This policy was implemented in 1816 by the introduction of internal improvements, a protective tariff, and the second Bank of the United States.
The same policies were continued under James Monroe. The Monroe Doctrine (1823), which proclaimed U.S. opposition to European intervention or colonization in the American hemisphere, introduced the long-continuing U.S. concern for the integrity of the Western Hemisphere. Domestically, the strength of the federal government was increased by the judicial decisions of John Marshall, who had already helped establish the power of the U.S. Supreme Court. By 1820, however, sectional differences were arousing political discord. The sections of the country had long been developing along independent lines.
In the North, merchants, manufacturers, inventors, farmers, and factory hands were busy with commerce, agricultural improvements, and the beginnings of the Industrial Revolution. In the South, Eli Whitney's cotton gin had brought in its wake a new staple; cotton was king, and the new states of Alabama, Louisiana, and Mississippi were the pride of the cotton kingdom. The accession of Florida (1819) further swelled the domain of the South. The American West was expanding as the frontier rapidly advanced. Around the turn of the century settlement of territory W of the Appalachians had given rise to the new states of Kentucky, Tennessee, and Ohio. Settlers continued to move farther west, and the frontier remained a molding force in American life.
The Missouri Compromise (1820) temporarily resolved the issue of slavery in new states, but under the presidency of John Quincy Adams sectional differences were aggravated. Particular friction, leading to the nullification movement, was created by the tariff of 1828, which was highly favorable to Northern manufacturing but a “Tariff of Abominations” to the agrarian South. In the 1820s and 30s the advance of democracy brought manhood suffrage to many states and virtual direct election of the President, and party nominating conventions replaced the caucus. Separation of church and state became virtually complete.