US acquisition of Mexican territory. Following the Mexican-American War and under pressure to construct a transcontinental railway across the south-west of the USA, the administration of President Pierce sent Senator James Gadsden to negotiate the necessary redefinition of the Mexico–US border. In the resulting transaction, Mexico was paid $10 million for ceding a strip of territory 76,767 sq km (29,640 sq miles) in the Mesilla Valley, south of the Gila River. The area completed the present borders of the mainland USA.
Subjects: World History — United States History.