Also as a result of the Mexican War, America gained two of the finest natural harbours in San Diego and San Francisco, which would eventually host major naval facilities as well as provide an outlet for propitious trade to the eastern countries. These outcomes show that the Mexican War provided many advantages for the Americans and proves that the accuracy of the prediction can be debated. The short and long-term economic benefits show that there were certainly positive effects of the war.
However it was also apparent that there was a high price for the war. It had cost almost $100 million and concluded with the deaths of more than 13000 American soldiers. Furthermore relations between America and Mexico remained tense for many decades, the distrust created by the war resulting in several military encounters along the border. Even during the war, there was growing debate over what to do in the event of territorial gains from Mexico. An important result of these discussions was the Wilmot Proviso, which, though defeated in the Senate in 1846 and 1847, revealed the anti-slavery feelings that was to slowly poison the relationship between the free states and the slave states. Because of the fundamental differences between the industrial North and agricultural South, the Mexican War was bound to cause problems and debates over which acquired states should be free and which should be slave.
It is shown that the Mexican War revived this controversy over the expansion of slavery. Ralph Waldo Emerson accurately predicts this and the ensuing sectional conflict which would eventually result in civil war. In fact, Congress' power itself was to be challenged by the Platform of the South, a response from the slave states to the Wilmot Proviso. The territorial gains from Mexico upset the delicate balance of power in the Senate between the free states and the slave states. The admission of the state of California as a free state threatened the South's ability to maintain this balance of power, and with it the ability to defend it's right to slavery. For them, slavery was their entire way of life, such was it integrated into their society that the attack on slavery was seen as an attack on their whole culture. As a result of land acquired from Mexico a growing secessionist movement in the South threatened the entire Union itself.
One of the best attempts to solve this issue came in the form of the 1850 Compromise. While neither side was completely happy with the terms it proposed, the Compromise managed to keep the Southern states from seceding at that time. While the Compromise seemed to provide a solution for peace, the land acquired from Mexico would again return to plague this, in the form of the Kansas-Nebraska Bill. It revived sectional tensions that would eventually lead to the secession of the Southern states. It seemed that the controversy raised by the Mexican War could not be quelled through peaceful means and the result was the American Civil War.
This nation defining struggle produced horrific casualties in what was regarded as the first full-scale modern war. It caused around 1.03 million deaths including 620000 soldiers in what was America's bloodiest conflict. As terrible as this outcome was, the victory of the Union over the Confederacy finally ended slavery within the conquered states and paved the way for America to truly embody the values of freedom and equality. The Civil War was essential in resolving the nation of a conflict neither side was willing to conclude through peaceful measures. Most interesting is the question of whether the effects of the Mexican War caused the Civil War to occur, or whether it served merely as a catalyst to accelerate a conflict that was eventually inevitable.
Although the prediction of Mexico poisoning America was true, there were many more aspects to it than that. The great wealth of the lands America acquired would prove to be an invaluable asset that would help develop it into an economic and continental superpower by the turn of the century. While the price was high, America recovered from the "poison" and became a stronger nation through the process. Ironically, the Mexican War produced effects that would eventually create a truly United States of America.
