74 Pa. Stat. § 120.108
Exclusive jurisdiction in and over the aforesaid lands is hereby ceded to the United States of America by the Commonwealth of Pennsylvania for the erection of forts, magazines, arsenals, dock yards, and other needful buildings, with the exception of roads abutting on said lands to be used by the United States for military and other public purposes, which are not already under the jurisdiction of the United States: And provided further, That the above cession is hereby made contingent upon the United States of America conveying to the Commonwealth of Pennsylvania all that tract of land conveyed by the Governor of Pennsylvania to the United States of America as will more fully appear by reference to deed dated October 19, 1917, and recorded in the office for the Recording of Deeds in and for Delaware County, in Deed Book number 387, page 581: And provided further, That the United States of America will relinquish the cession of jurisdiction therein granted by the Commonwealth of Pennsylvania.
74 P.S. § 120.108