What happened that caused the Mexican Cession to occur?

The Mexican Cession occurred as a result of the Mexican-American War, which took place from 1846 to 1848. The war began over disputes regarding the Texas-Mexico border following the annexation of Texas by the United States in 1845, which Mexico considered an act of aggression.

Here's a summary of the events leading up to the Mexican Cession:

1. Texas Annexation: In 1845, the United States annexed the Republic of Texas, which had gained independence from Mexico in 1836. Mexico viewed this annexation as an encroachment on its territory, as it still considered Texas to be part of Mexico.

2. Border Disputes: There was disagreement between the United States and Mexico over the location of the Texas border. The United States claimed the Rio Grande as the boundary, while Mexico asserted that the Nueces River was the true boundary.

3. Diplomatic Tensions: Diplomatic relations between the United States and Mexico deteriorated due to the annexation of Texas and other issues, including the treatment of Mexican Americans in the annexed territory.

4. Outbreak of War: In April 1846, the United States and Mexico went to war over the disputed territory. The U.S. forces, led by General Zachary Taylor, invaded Texas and secured several victories.

5. Zachary Taylor's Successes: Taylor's forces won a series of battles in northern Mexico, including the Battle of Monterrey in September 1846.

6. Winfield Scott's Invasion: In March 1847, another U.S. force led by General Winfield Scott landed at Veracruz and marched towards Mexico City. Scott defeated the Mexican army in several battles, including the Battle of Cerro Gordo in April 1847 and the Battle of Churubusco in August 1847.

7. Mexico City captured: U.S. forces under Scott eventually captured Mexico City in September 1847. The Mexican government relocated to Querétaro, but continued to resist the American occupation.

8. Treaty of Guadalupe Hidalgo: In February 1848, the Treaty of Guadalupe Hidalgo was signed, officially ending the Mexican-American War. Under the terms of the treaty, Mexico ceded a vast territory to the United States, including the present-day states of California, Nevada, Utah, Arizona, New Mexico, and parts of Colorado and Wyoming.

The Mexican Cession resulted in the United States acquiring a significant amount of land from Mexico, increasing its territory by approximately one-third. It also led to significant changes in the demographics, culture, and politics of the acquired regions, as well as ongoing debates and discussions about border disputes and historical narratives related to the war and the treaty.