The Mexican-American War was fought between the United States and Mexico from 1846 to 1848, largely over Texas, the Rio Grande border, and U.S. expansion westward. The war ended with the Treaty of Guadalupe Hidalgo, by which Mexico ceded a huge amount of territory to the United States, including land that later became California, Nevada, Utah, Arizona, and parts of several other states.britannica
The result was important because it dramatically expanded the United States by more than 500,000 square miles, about a third of the country’s size at the time. It also intensified debates in the U.S. over slavery, since the new western lands raised the question of whether slavery would spread into them.britannica+1
James K. Polk, the president who pushed the war and western expansion.websites.umich+1
Zachary Taylor, the general whose forces fought key early battles and later became a national hero.websites.umich+1
Winfield Scott, who led the campaign from Veracruz to Mexico City and helped bring the war to an end.websites.umich
Stephen W. Kearny, who occupied New Mexico and California.britannica
The main causes were the annexation of Texas, disagreement over whether the border was the Nueces River or the Rio Grande, and the broader idea of Manifest Destiny. The conflict ended in 1848 when Mexico accepted defeat and signed the treaty that transferred the territory to the United States.exploros+3
If you want, I can turn this into a short school-style paragraph or a bullet-point study note.