After the Missouri Compromise, events took the politics of slavery off center stage, replaced by American relations with Mexico. In 1835-1836, Texas declared its independence from Mexico and began the fight that would lead to the eventual forming of the Republic of Texas. One of the reasons that the Texans pushed for independence was that the state that it belonged to, Coahuila y Tejas, endorsed a plan for the gradual emancipation of the state’s slaves in 1827, which angered many slaveholding settlers who had moved to Texas from the South.
By 1845, Texas had consented to annexation by the United States. This action spawned a number of border disputes with Mexico, leading to the Mexican-American War that lasted from April 25, 1846 to February 2, 1848.
The Treaty of Guadalupe Hidalgo, signed on February 2, 1848, ended the war and gave the U.S. undisputed control of Texas, established the U.S.-Mexican border of the Rio Grande River, and ceded to the United States the present-day states of California, Nevada, Utah, New Mexico, most of Arizona and Colorado, and parts of Texas, Oklahoma, Kansas, and Wyoming. In return, Mexico received US $18,250,000 and the U.S. agreed to assume $3.25-million in debts that the Mexican government owed to U.S. citizens.
The territorial gains from the Mexican-American War was to create a new set of slave-state-free state conflicts between the North and the South. Both sides tried to gain the upper hand with various attempts to either expand slavery or curtail the institution.
The Wilmot Proviso would have banned slavery in any territory to be acquired from Mexico in the Mexican-American War or in the future, including the area later known as the Mexican Cession, but which some proponents construed to also include the disputed lands in south Texas and New Mexico east of the Rio Grande.
The Proviso was an amendment that David Wilmot, a Democratic congressman from Pennsylvania, introduced the amendment on August 8, 1846 as a rider on a $2,000,000 appropriations bill intended for the final negotiations to resolve the Mexican–American War, despite the fact that this was only 3 months into the 2 year war. It passed the House but failed in the Senate, where the South had greater representation. Reintroduced in February 1847, it again passed the House and failed in the Senate. In 1848, an attempt to make it part of the Treaty of Guadalupe Hidalgo also failed.
The Compromise of 1850 was an extremely complex and comprehensive attempt to resolve many of the differences between the North and the South. A package of 5 bills it was passed in September 1850. Each of the five bills in some way touched on the slavery issue.
- California was admitted to the Union as a free state.
- The slave trade was abolished (the sale of slaves, not the institution of slavery) in the District of Columbia.
- The Territory of New Mexico (including present-day Arizona) and the Territory of Utah were organized under the rule of popular sovereignty. This meant that the citizens of the territories could decide whether to be slave states or free.
- A harsher Fugitive Slave Act was passed by the Senate 27-12, and by the House 109-75.
- Texas gave up much of the western land that it claimed and received compensation of $10,000,000 to pay off its national debt.
The opinions of historians on the Compromise of 1850 vary widely. Some say that it postponed the Civil War for a decade. It was during this decade from 1850 until 1860 that the Northwest grew dramatically and became firmly allied politically with the Northeast. The decade also brought about the dissolution of the Whig Party with its replacement in the North by the new Republican Party and in the South by the Democrats.
Others point out that the Fugitive Slave Law polarized and divided the North and the South. The northern reaction to Harriet Beecher Stowe‘s novel Uncle Tom’s Cabin was the most obvious response to the law.
The delay of hostilities by a decade allowed the further industrialization of the North with its many more miles of railroad, steel production, modern factories, and population than the South which was tied to its rural, slave-based economy.
In 1854, the Ostend Manifesto was a document that outlined the reasons why Cuba should be acquired by the United States. The main driving forces behind this document were the debates over slavery in the United States, Manifest Destiny, and the Monroe Doctrine. It ignited the north-south fight over the expansion of slavery once again. During the period that would come to be known as Bleeding Kansas, it served as a rallying cry for the enemies of the Slave Power. The movement to annex Cuba wasn’t effectively ended until after the American Civil War.