Missouri Compromise -
Mexican War -
Missouri Compromise was an agreement passed by the U.S. Congress in 1820 to maintain a balance between free and slave states. It allowed Missouri to enter the Union as a slave state, but also prohibited the expansion of slavery in the northern portion of the Louisiana Purchase territory above the 36°30' parallel.
Mexican War was a conflict fought between the United States and Mexico from 1846 to 1848. It was sparked by a dispute over the border between Texas (which had recently been annexed by the U.S.) and Mexico. The U.S. believed the border was at the Rio Grande, while Mexico claimed it was the Nueces River. The war ended with the Treaty of Guadalupe Hidalgo, in which Mexico ceded a significant amount of territory to the United States, including present-day California, Nevada, Utah, Arizona, New Mexico, and parts of Colorado, Wyoming, Kansas, and Oklahoma.