Task: Text Simplification
Input (English): 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 .
Output (English): The Arizona Territory was an American territory from February 24 , 1863 to February 14 , 1912 .