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 federal properties within the state border or tax non-residents at a rate higher than residents, and would have a republican form of government, and also after reaching a population equal to that of the least-populated of the established states, it would be admitted, on an equal footing with all other states, based on a majority vote in Congress. Jefferson's original draft of the ordinance gave names to the proposed states, and also contained a provision that "After the year 1800 there shall be neither slavery nor involuntary servitude in any of them." The 1784 ordinance was superseded three years later