Arizona Territory 1877. The capital was finally moved to Phoenix on February 4, 1889. The territory was admitted to the Union as the 48th state on February 14, 1912. Proclamation to the People of Arizona. Arizona Territory The Territory of Arizona (also known as Arizona Territory) was a territory of the United States that existed from February 24, 1863 until February 14, 1912, when the remaining extent of the territory was admitted to the Union as the state of Arizona. It was created from the western half of the New Mexico Territory during the American Civil War. Following the expansion of the
Admission to the Union enabling act was a common historic practice, a number of states were admitted to the Union without one. In many instances, an enabling act would detail the mechanism by which the territory would be admitted as a state following ratification of their constitution and election of state officers. Although the use of such an act is a traditional historic practice, a number of territories have drafted constitutions for submission to Congress absent an enabling act and were subsequently admitted. The broad outline for this process was established by the Land Ordinance of 1784 and the 1787 Northwest Ordinance, both of