Mexican Cession

The Mexican Cession of 1848 is a historical name in the United States for the region of the modern day southwestern United States that Mexico ceded to the U.S. in the Treaty of Guadalupe Hidalgo in 1848, but had not been part of the areas east of the Rio Grande which had been claimed by the Republic, though the Texas annexation resolution two years earlier had not specified Texas's southern and western boundary. The Mexican Cession was the second largest acquisition of territory in the US history of 520,000 sq. miles. The largest was the Louisianian Purchase with some 820,000 sq. miles.

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