There were several events leading up to the Mexican-American War, and several consequences that resulted from it.
Spain had held colonial interests in America since the 1540s. This is even before Great Britain had colonial interest in America. So, Spain had been there a long time.
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In 1821, Mexico revolted against Spain and became a free nation. So, Mexico kind of did what America did. They said, “We’re tired of Spain ruling us from across the ocean. They’re not letting us do what we want to do over here. We’re over here, we want to be a free nation. We’re declaring ourselves a free nation, and we’re going to revolt against Spain until we become a free nation.” That’s what they did, and in 1821, they had won their independence.
Well, in 1836, Texas followed suit, and Texas became an independent nation after revolting against Mexico. So, Texas had been a part of Mexico, and therefore, under Spanish rule before then for a long time. But, Texas had more settlers coming in from America, and Texas had a different outlook on things. They wanted to rule themselves, they wanted to make up their own laws, they didn’t want to have to follow Mexico’s laws. And Mexico’s government was centered very far away from Texas, and so, it was harder for them to enforce things there, and Texas finally said, “You know what, we want to be an independent nation. Mexico revolted against Spain, now we’re going to revolt against Mexico.” And in 1836, they had won their independence from Mexico and became an independent nation.
In 1845, Texas was annexed by the United States, which was agreed to by President Tyler. So, Texas was an independent nation. All by itself, its own governing nation. But, Texas was close to America, and it was also close to Mexico, and their government and their ideas aligned more closely with the United States, and so, they decided they would like to be annexed by the United States. They would like to become a state in the Union. And in 1845, that happened after President Tyler agreed to it.
In 1846, Mexico and America went to war, and there were a few things besides all this that led up to that. Mexico owed the United States $4.5 million from their war for independence. So, Mexico revolted against Spain, they had borrowed money, food, weapons from the United States, and so, they owed them $4.5 million. President Polk offered to forgive the debt in exchange for land: New Mexico and Upper California. But Mexico refused. Well, the United States wasn’t going to declare war just for that, but that did create some tension between the two countries.
Then, Mexicans attacked American troops along the Southern border of Texas. Texas was now a state in the United States. And so, these American troops in this state that was part of America were attacked by Mexicans, and so, America attacked back. The war went on for a while, and during that time, there were some of other issues that arose and became prominent.
More conflict arose over the Wilmot Proviso, which stated that slavery would be banned in any additional territory acquired from Mexico, as well as in any other future acquisitions. So, at this point, there were slave states, and there were free states. And Congressman Wilmot headed up this bill and he said he wanted this signed, and it was tacked on to anything that was going to help in this war, because they didn’t want to let the war end without being determined if this new territory would be eligible to have slaves go and work there, or if it was going to be all free states that were gained after the war. And Wilmot and his supporters all said slavery ought to be banned in any additional territory.
Well, slave states didn’t like this because the slave states had a certain number of states, and free states had a certain number of states, and those pretty evenly matched. If there were no more slave states allowed, then it was going to be more free states out numbering the slave states. The slave states didn’t want to lose their slaves because that’s where a lot of their economy came from. The slaves worked on their plantations and grew different crops, primarily cotton in the South, and worked in other various jobs, but they weren’t paid anything. If the South and the other slave states lost that source of labor, they were going to have to start paying the slaves to do that, or come up with some other solution. So, the slave states really didn’t like this provision, and the free states did. And so, there was a lot of conflict there, and it was hard to get this past.
And in the end, the Wilmot Proviso wasn’t what was passed. The war ended in 1848 with the Treaty of Guadalupe Hidalgo, which is where the surrender and treaty terms were worked up by Guadalupe Hidalgo. And these are the things that Mexico and America agreed on.
The United States paid $15 million to Mexico, and agreed to pay off claims up to $3.25 million. And those were claims of American citizens against Mexico, that Mexico owed them land or goods or money. The United States agreed to pay off those claims for Mexico up to $3.25 million. Anything over that that was being claimed Mexico owed them, Mexico would be required to pay.
The next part is that the United States gained California and a large area containing New Mexico, Nevada, Arizona, Utah, and parts of Colorado and Wyoming. Mexicans living in this area were given a choice. They were allowed to relocate to Mexico, or they could become full American citizens with all the full set of civil rights entitled to them. And over 90% of them stayed. They decided it would be better to stay in America in these newly formed states, and that would be better than going back to Mexico.
The Rio Grande River was established as a Southern boundary for Texas. That is one of the borders that had been being disputed very heavily, and where the first attacks of the Mexican-American War were, and so, the border was finally established. The Rio Grande River would be the boundary between Texas and Mexico, and therefore, the United States and Mexico in that area.
So, the Mexican-American War was fought between Mexico and America right after Texas was annexed when they were still unsure about the boundary, and in the end, the United States gained a lot of land out of this treaty – the Treaty of Guadalupe Hidalgo – that ended the Mexican-American War