The Mexican-American War, which occurred between 1846 and 1848, ended with the Treaty of Guadalupe Hidalgo. This treaty ceded a significant portion of Mexican territory to the United States, including present-day California, Arizona, New Mexico, Nevada, Utah, and parts of Colorado and Wyoming. The result markedly increased U.S. territory and fulfilled the concept of Manifest Destiny, the belief that the U.S. was destined to expand across the continent. However, the acquisition of new territories intensified the debates over slavery, contributing to the sectional conflicts that would eventually lead to the Civil War.