The board of directors, after a county free library is established, shall annually levy in the same manner and at the same time as other county secondary property taxes are levied a county free library district tax sufficient to establish the district and to insure the payment of salaries, maintenance and upkeep and other necessary expenses of the county free library district. The tax shall be levied and collected upon all property in the county and upon all property within incorporated cities and towns in the county.
A.R.S. § 48-3903