 In February of 1846, Anson Jones lowered the flag and declared the Republic of Texas was now over. In the years following, he became despondent at the end of the Republic and later on committed suicide in 1858. But many people were happy that Texas became a new part of the United States, and they thought that things would be better. In just a few years, everything that Andrew Jackson had warned about would come to pass, fears over slavery and problems with Mexico. The U.S. Mexican War is an often overlooked part of American history and certainly an often ignored part of Texas history. But this is really the war that actually made Texas part of the United States. And ended all claims Mexico had to the property between the Rio Grande and the Nueces River. President James K. Polk was elected in 1844 and he came in March of 1845 as the heir apparent to Andrew Jackson. Polk's nickname was Young Hickory. He was seen as being the continuation of the Jackson style of government. And he was an expansionist. He believed that America should reach from sea to sea. And so he was eager to gain more territory for the United States. This is evident in his expansionism of the Northwest. Here we see a map of the Oregon Territory. We know that the Adams and East Line was signed in 1819, that Transcontinental Treaty, which drew the line of the 42nd Parallel. That was a northern boundary in that territory. This Oregon Territory above was contested between the Russians, the British, and the United States. We had a line of 1818 that brought the United States over along the Missouri River to what's today Idaho. But many Americans wanted more. There was the feeling that there was gold up in the territory. There was certainly a lot of trade in the fur trade going on in that area. Great Britain was certainly earning a lot of money in the fur trade. And so other people were trying to get into that market. And so this 5440 or fight, many Americans wanted the territory up to the 5440 line. Now Great Britain wasn't willing to do that. It would meant encroachment and maybe the end of their hegemony in the fur trade in the Pacific Northwest. President Polk would have been happy with the line of 1818 being extended. And so he threatened to go to war with Great Britain using the Battle Cry 5440 or fight. Well, Great Britain backed down. They didn't want to go to war. So they sent in negotiators and settled on an extension of that 1818 line. That's exactly what Polk had wanted. And so he got what he wanted by rattling the sabers a little bit. That very same year in 1846, Zachary Taylor was sent down to Corpus Christi and then moved down to the Rio Grande. General Taylor had orders from the president to march around the Rio Grande near Matamorris Brownsville area. Mexican troops were there to prevent any incursions and we don't know who, but somebody fired a shot. On May 13th, Congress declared war. President Polk said famously that American blood had been shed on American soil. And some people in Congress simply did not believe that. The so-called spot resolution was introduced asking the president to show Congress the place where American blood was shed. It was actually in disputed territory and people like Abraham Lincoln and others were very much against war, especially war that had the possibility of spreading slavery. In June of 46, the president sent John C. Fremont and Kit Carson into California. A U.S. Pacific squadron was sent to California as well to the coasts around San Francisco and San Diego and Los Angeles. And also ground troops, Stephen Kearney, took Santa Fe and moved toward Los Angeles along in what's today New Mexico. So it was a three-pronged attack upon Mexican territory. So as the war begins, Zachary Taylor moves to Matamorris and to Monterey. Santa Ana, who is in exile in Cuba, negotiates to be brought back to Mexico City in order to help the country fight the war. Zachary Taylor and Santa Ana meet at Buenavista and there are battles going on there and then Santa Ana goes back to Mexico City. Scott moves down to Vera Cruz by March of that year and he's in Mexico City by mid-September. Santa Ana and the Mexican Congress flee the city and the United States takes over and occupies Mexico City. The Treaty of Guadalupe de Algo is signed early in the next year, although the fighting ended by mid-September. But by the time this treaty is signed, it brings a great amount of land over 1.2 million acres into the United States. And it set the Rio Grande as a southern border. It also allowed full citizenship for any Mexicans who decided to become American citizens and remain in the United States. And this is the beginning of Mexican Americans. New Mexico and California would also go to the United States and the United States would pay Mexico $15 million for all the land that it got. And so the acquisition of this more than a million acres of land raises questions that are going to have to be sorted out in Congress. And some of the questions are over slavery. Would the new territory be open to slavery or would it be closed to slavery and only open to free settlers? So if you brought in more slaves, it's going to upset the balance of power in Congress. And there was a question over this large western land. How would the size of states like California and Texas affect the balance of power? Hopefully these would be worked out. There was an election in 1848 and the hero of the U.S.-Mexican War, Zachary Taylor, old, rough and ready, became the president. And he was really an example of the contradictory forces at work in the United States at the time. He was a slave owner, but he wasn't opposed to letting California and New Mexico become free states. He was a southerner, but he believed in the United States and in nationalism. And many of his actions angered people from the different sections, angered both North and South. He ignored the call for a fugitive slave law, which upset the South. But at the same time, he upset the North by ignoring calls to abolish slavery in D.C. When he died on July 9th, 1850, Congress was still trying to sort out the problems of the U.S.-Mexican War and all the land. Finally, a compromise was settled upon in 1850 and it was the last time a compromise would be struck over the issues facing the sectional crisis. Miller Fillmore was president at the time and he worked with Illinois Senator Stephen Douglas on the compromise of 1850 to get this passed and signed. And so California would come in as a free state. Texas would reduce its size in exchange for $10 million and it would not have claimed a Santa Fe anymore. The compromise of 1850 also pleased the South in providing for a stronger fugitive slave law and it did abolish the slave trade in Washington, D.C. In the aftermath of the U.S.-Mexican War, Congress was ultimately affected but there were still attempts to maintain a balance. And you'll see this especially in the Senate. The Senate is the more powerful House. The Senate is the more powerful chamber in Congress and so it wanted to maintain a balance between Northern and South between slave and free states. And so you see the slave states had 90 reps but 30 senators. The free states had 141 reps but 32 senators. So they had a few more delegates in the House but about an even amount of senators as did the slave states. And so this balance was very important. So the compromise of 1850 is the last time you're going to see these sectional divisions able to work out a compromise before it leads to civil war.