The Treaty of Guadalupe Hidalgo (1848):

The Treaty of Guadalupe Hidalgo ended the Mexican-American War and transferred a large area of Mexican territory to the United States. Under the treaty, the United States paid Mexico $15 million for the Mexican Cession; Mexico did not pay the United States. The treaty did not complete all continental expansion, since the United States later acquired additional territory, including the Gadsden Purchase.

AI-written and checked against the verified answer.