Answer: The Gadsden Purchase, or Treaty, was an agreement between the United States and Mexico, finalized in 1854, in which the United States agreed to pay Mexico $10 million for a 29,670 square mile portion of Mexico that later became part of Arizona and New Mexico.
The idea of manifest destiny greatly helped shape the U.S. governments's policies of land acquisition, since this held that the US was "destined" to expand from the Atlantic Ocean to the Pacific--meaning that the US embarked on a series of wars with Mexico and confrontations with Natives that helped the settlers move west.
