53 Pa. Stat. § 25900
When the board of assessors shall have altered and amended the lists of all taxable property so as to arrive at its true cash value, they shall then ascertain the aggregate amount of the value of the entire taxable property of said city, which valuation shall remain the lawful valuation for purposes of city taxation until altered as herein provided; the said board then shall proceed to classify the real estate so assessed in such manner and upon such testimony as may be adduced before them, so as to discriminate between built-up property, rural or suburban property, and property used exclusively for agricultural or farm purposes, including untillable land, respectively, and to certify to the councils of said city, during the month of January of each year, the aggregate valuation of city, rural and agricultural property subject to taxation, and in so classifying said property the character shall determine its classification. It shall be the duty of said councils in determining the rate of taxation for each year to assess a tax upon said agricultural, farm or untillable land equal to one-third the highest rate of tax required to be assessed for said year, and upon said rural or suburban property a tax not exceeding two-thirds of the highest rate required to be assessed as aforesaid, and upon said built-up property a tax equal to the highest rate required to be assessed as aforesaid. So that upon the said classes of real estate of said city there shall be three rates of taxation.
53 P.S. § 25900