Created 1860 by an Act of Legislature of New Mexico, of which the present state was then a part. Act reads: "All that part of the Territory of New Mexico situated west of a line running due north and south from northern to southern boundary line of Dona Ana county, through a point one mile distant easterly from what is called the Overland Stage Mail Station, to the Apache Caves, shall be and hereby is, created into a county to be called and known as the county of Arizona." Northern line was apparently the Gila river. Tubac was the county seat; population 2,697. An Act of July 8, 1861, changed the county seat to Tucson.