Pennsylvania Statutes Title 51 Pa.C.S.A. Military Affairs § 301. Formation

(1) all able-bodied citizens of the United States and all other able-bodied persons who have declared their intention to become citizens of the United States, residing within this Commonwealth, who are at least 17 years six months of age and, except as hereinafter provided, not more than 55 years of age; and

(2) such other persons as may, upon their own application, be enlisted or commissioned therein.