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 formed in the Northwest Territory under either ordinance. In August, 1789, the ordinance was replaced by the Northwest Ordinance of 1789, in which the new Congress (under the present Constitution) reaffirmed the Ordinance with slight modifications. The territory itself remained in existence until 1803, when the southeastern portion of it was admitted to the Union as the State of Ohio, and the remainder was reorganized. While the articles of Confederation were in effect, the Congress considered various ordinances admitting particular new states into the Union, none of which were approved: At the 1787 Constitutional Convention, a proposal to include the