The basic principles governing application of the Equal Protection Clause of the Fourteenth Amendment are familiar. See Reed v. Reed, 404 U. S. 71, 404 U. S. 75-76 (1971): 'In applying that clause, this Court has consistently recognized that the Fourteenth Amendment does not deny to States the power to treat different classes of persons in different ways. Barbier v. Connolly, 113 U. S. 27 (1885); Lindsley v. Natural Carbonic Gas Co., 220 U. S. 61 (1911); Railway Express Agency v. New York, 336 U. S. 106 (1949); McDonald v. Board of Election Commissioners, 394 U. S. 802 (1969). The Equal Protection Clause of that amendment does, however, deny to States the power to legislate that different treatment be accorded to persons placed by a statute into different classes on the basis of criteria wholly unrelated to the objective of that statute. A classification' 'must be reasonable, not arbitrary, and must rest upon some ground of difference having a fair and substantial relation to the object of the legislation, so that all persons similarly circumstanced shall be treated alike.' 'Royster Guano Co. v. Virginia, 253 U. S. 412, 253 U. S. 415 (1920).'