Gadsden Purchase
In 1861, during the American Civil War, the Confederate States of America formed the Confederate Territory of Arizona, including in the new territory mainly areas acquired by the Gadsden Purchase. In 1863, using a north-to-south dividing line, the Union created its own Arizona Territory out of the western half of the New Mexico Territory. The new American Arizona Territory also included most of the lands acquired in the Gadsden Purchase. This territory would be admitted into the Union as the State of Arizona on February 14, 1912, the last area of the Lower 48 States to receive statehood.