Answer the following Q with stream of consciousness. Passage: 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. It had not been part of the areas east of the Rio Grande which had been claimed by the Republic of Texas, though the Texas annexation resolution two years earlier had not specified the southern and western boundary of Texas. The Mexican Cession (529,000 sq. miles) was the third largest acquisition of territory in US history. The largest was the Louisiana Purchase, with some 827,000 sq. miles, followed by the acquisition of Alaska (about 586,000 sq. miles).

Question: Based on this passage, when was the mexican cession added to the united states?
The relevant information is: 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. Therefore, the final answer is 1848.