Gadsden Purchase
The state (like its southwestern neighbors) has had close linguistic and cultural ties with Mexico. The state outside the Gadsden Purchase of 1853 was part of the New Mexico Territory until 1863, when the western half was made into the Arizona Territory. The area of the former Gadsden Purchase contained a majority of Spanish-speakers until the 1940s, although the Tucson area had a higher ratio of anglophones (including Mexican Americans who were fluent in English); the continuous arrival of Mexican settlers increases the number of Spanish speakers.