Arizona's journey to statehood traces back to its acquisition by the United States from Mexico in 1848, following the conclusion of the Mexican-American War. This acquisition, solidified by the Treaty of Guadalupe Hidalgo, saw a vast expanse of land, including what would become Arizona, incorporated into the United States. However, it wasn't until 1853 that further expansion occurred with the Gadsden Purchase, which added additional territory, primarily in the southern region of present-day Arizona. This strategic acquisition was primarily aimed at facilitating the construction of a southern transcontinental railroad route.

The establishment of Arizona Territory on February 24, 1863, marked a significant milestone in the region's governance. The territory was carved out of the western portion of the New Mexico Territory to better administer the growing population and address the unique needs of the area. With this creation, Arizona began to develop its own distinct identity, separate from its neighboring territories.

However, Arizona's territorial boundaries underwent further adjustments in 1866 when portions of land situated north and west of the Colorado River were ceded to Nevada. This alteration aimed to streamline administrative responsibilities and ensure more efficient governance in the respective territories. Consequently, this adjustment resulted in the boundary configuration that closely resembles the present borders of Arizona.

Despite not officially attaining territorial status until 1863, census data for Arizona are available as early as the 1860 census. These early records provide valuable insights into the demographic composition and settlement patterns of the region during its formative years. Any revisions or discrepancies in the population data from the 1860 census are meticulously documented and explained in historical records, such as Richard L. Forstall's comprehensive study on population demographics in the United States.

The transition from territorial status to statehood culminated in Arizona's admission to the Union on February 14, 1912, as the 48th state. This milestone represented the culmination of decades of development, struggle, and perseverance by the residents of Arizona. With statehood, Arizona gained full autonomy and representation within the federal government, solidifying its place as an integral part of the United States.

The availability of census data became more standardized with the official recognition of Arizona as a state, starting from the 1920 census. This marked a new chapter in the recording and analysis of demographic trends, providing valuable information for policymakers, researchers, and historians alike. Through the lens of census records, the evolution of Arizona's population and societal dynamics can be traced, offering valuable insights into its past, present, and future.