What was the main result of the Treaty of Guadalupe Hidalgo?

The Treaty of Guadalupe Hidalgo, signed in 1848, was a pivotal agreement that marked the end of the Mexican-American War. The main result of this treaty was indeed the acquisition of significant territories by the United States from Mexico. As part of the treaty's terms, Mexico ceded a vast area that included present-day California, Nevada, Utah, Arizona, New Mexico, and parts of Colorado and Wyoming. This territorial expansion was instrumental in fulfilling the concept of Manifest Destiny, which held that the U.S. was destined to expand across the North American continent.

The other choices do not relate to the treaty’s outcomes. The end of the Civil War pertains to a different historical period altogether, as that conflict took place between 1861 and 1865, well after the treaty was signed. The Monroe Doctrine was established in 1823 and dealt with European interference in the Americas, unrelated to the territorial changes following the 1848 treaty. Lastly, the Spanish-American War occurred in 1898, also not connected to the consequences of the Treaty of Guadalupe Hidalgo. Thus, the correct answer captures the treaty's significant impact on the territorial map of the United States post-war.