Heading Toward the Civil War and Reconstruction (1845-1877)

James Polk, a "war hawk" as a young man and a Democrat expansionist, was pitted against the Whig leader Henry Clay in the election of 1844. James was an expansionist because he wanted to expand the Northwestern border deep in Canadian territory. Polk won the election, thus making President Tyler to propose the annexation of Texas because he thought James Polk would mandate for annexation with his victory. Polk negotiated the American-Canadian border with reasoning. Great Britain signed the Oregon Treaty in 1846 to allow the United States to acquire Oregon, Washington, without the need for conflict/war. Polk tried buying the Southwest territory from Mexico, but failed to do so. Polk provoked the attack on American troops by Mexico, and Mexico was already provoked by the annexation of Texas. Congress granted the ability to James Polk to wage war in 1846: the Mexican-American War. Whigs members questioned the declaration of war, and if Mexico fired first.

Many Americans did not support the war because they feared that the new intact states of the West would become slave states. Some opponents thought that James Polk supported slaveholders because he declared war to gain the states, and some Americans believed that some slave owners had control over the government. These rich Southerners were defined as Slave Power by abolitionists; a symbol.

The gag rule of 1836, which forbids members of the legislative or decision-making body to raise topics or to consider discussions, raised suspicions of Slave Power. The Wilmot Proviso, a bill that prohibited the expansion of slavery to the new states that were to be gained, was not passed, and thus raised further suspicion. The decline of the bill caused the Free-Soil Party to be formed. The Free-Soil Party was a party that focused on the issues discussed in the Wilmot Proviso, and looked forward to fulfill what the bill meant to accomplish. Southerners were still insistent that the extension of slavery in the South should not be restricted.

The Mexican-American War had the United States winning because troops were taking over Texas, sent to California, and then tasked to invade Mexico City. The Treaty of Guadalupe Hidalgo (1848) gave up the Southwest that belonged to Mexico, such as Arizona, New Mexico, California, Nevada, and Utah. The new territory increased the wealth of the United States, but slavery was still a problem. The Democrats supported the South, and displayed that slavery would be allowed to be extended. Popular sovereignty would solve the issue on the decision of slavery status on the new states. Popular sovereignty meant that the territories would decide by vote, whether to refuse or allow slavery. The Whigs did not oppose slavery, so the party was divided into sections that favored or declined slavery. The Antislavery Whigs joined the Free-Soil Party. The Whigs won the presidential election of 1848 by running Zachary Taylor. The powerful Whigs leaders, Daniel Webster and Henry Clay, died before the election of 1852, marking the descent of the Whigs party. The Republican party was to rise.