74 Pa. Stat. § 1
The jurisdiction of this State is hereby ceded to the United States of America over all such pieces or parcels of land, not exceeding ten acres in any one township, ward or city, or borough, within the limits of this State, as have been or shall hereafter be selected and acquired by the United States for the purpose of erecting post offices, custom houses or other structures, exclusively owned by the general government, and used for its purposes: Provided, That an accurate description and plan of such lands, so acquired, verified by the oath of some officer of the general government having knowledge of the facts, shall be filed with the Department of Internal Affairs of this State, as soon as said United States shall have acquired possession of the same.
All such descriptions and plans heretofore filed with the Secretary of the Commonwealth shall, as soon as it may conveniently be done, be transferred to the Department of Internal Affairs, and the Department of Internal Affairs shall give to the Secretary of the Commonwealth proper receipts for such descriptions and plans.
The jurisdiction so ceded to the United States of America is granted upon the express condition that the Commonwealth of Pennsylvania shall retain concurrent jurisdiction, with the United States in and over the lands and buildings aforesaid, in so far that civil process in all cases, and such criminal process as may issue under the authority of the Commonwealth of Pennsylvania against anyone charged with crime committed outside said land, may be executed thereon in the same manner as if this jurisdiction had not been ceded. The United States shall retain such jurisdiction so long as the said land shall be used for the purposes for which jurisdiction is ceded and no longer.
The jurisdiction so ceded to the United States shall be upon the further condition that the Commonwealth reserves to itself and its political subdivisions whatever power of taxation it may constitutionally reserve, to levy and collect all taxes now or hereafter imposed by the Commonwealth and its political subdivisions upon property, persons, and franchises within the boundaries so ceded.
74 P.S. § 1