Summary
Highlights
The 1840 election saw the Whigs elect William Henry Harrison, with John Tyler, a former Democrat, as his vice president. Harrison died 32 days into his term, making Tyler president. Tyler, holding many Democratic beliefs, clashed with the Whig party, vetoing their bills and causing his cabinet to resign. He attempted to annex Texas to gain support, but this was defeated by Whigs in Congress who opposed adding more slave states.
In 1844, James K. Polk, a 'dark horse' candidate, won the presidency against Henry Clay. Polk campaigned on the annexation of Texas, which was accomplished by a joint resolution pushed through by lame-duck President John Tyler just before Polk took office. Polk's other goals included lowering tariffs, and most significantly, national expansion under the banner of Manifest Destiny, aiming to acquire Oregon and California.
Manifest Destiny was the belief that America was destined to conquer and civilize the entire continent from coast to coast, often ignoring existing populations. This concept, coined by John O'Sullivan in 1845, fueled western expansion, a long-standing American trend. However, in the 1840s, the issue of slavery increasingly complicated this expansion, resurfacing debates previously settled like the Missouri Compromise.
Polk's campaign slogan, '54-40 or fight,' highlighted his ambition to claim the entire Oregon Territory. Despite joint occupation with England since 1818, increased American settlement along the Oregon Trail pressured the issue. Ultimately, the Oregon Treaty of 1846 peacefully resolved the dispute, establishing the 49th parallel as the boundary between the US and Canada, with England retaining fishing rights around Vancouver Island.
Mexico still considered Texas its territory and disputed the boundary, claiming the Nueces River rather than the Rio Grande. Polk's attempts to purchase California were rebuffed by Mexico. Tensions escalated when Polk sent Zachary Taylor into the disputed territory, leading to an attack on US forces in April 1846, which sparked the Mexican-American War.
The Mexican-American War was highly controversial in the North, with many viewing it as a Southern attempt to expand slavery. Abraham Lincoln questioned the validity of the initial attack with his 'Spot Resolution,' and David Wilmot's failed 'Wilmot Proviso' sought to ban slavery in any acquired Mexican territories. The war ended with the Treaty of Guadalupe Hidalgo in 1848. The US gained California, New Mexico, and other Southwestern territories, increasing its land by one-third and establishing the Rio Grande as the border. This significant land acquisition, however, intensified the debate over slavery in new territories, bringing it back to the forefront of national politics.