The same clause of the Constitution which grants to Congress exclusive jurisdiction over the district to be selected for the seat of the National Government, authorizes Congress "to exercise like authority over all places purchased by the consent of the legislature of the State in which the same shall be for the erection of forts, magazines, arsenals, dockyards, and other needful buildings."

The federal ownership of such tracts within the States is to be sharply distinguished from political jurisdiction over them. This latter, as the Constitution provides, may be obtained only when the districts have been acquired with the consent of the States in which they are situated.

The language of Clause 17 would seem to indicate that the framers of the Constitution intended that the General Government should or could acquire lands within the States only by purchase and with the consent of the States. In practice, however, this consent has not always been obtained, or been deemed necessary. But, in such cases, the political jurisdiction of the State is not ousted, unless the lands are used for the purposes of government. In Fort Leavenworth R. R. Co. v. Lowe12 the court say: "The consent of the States to the purchase of lands within them for the special purposes named [in Clause 17] is . . . essential under the Constitution, to the transfer to the General Government with the title, of political jurisdiction and dominion. Where lands are acquired without such consent, the possession of the United States, unless political jurisdiction be ceded to them in some other way, is simply that of an ordinary proprietor. The property in that case, unless used as a means to carry out the purposes of the government, is subject to the legislative authority and control of the States equally with the property of private individuals."

Also, the General Government is able to acquire lands within the States by the exercise of the right of eminent domain, a right which it may employ when "necessary and proper " to the exercise of any of its expressly given powers.13 When thus obtained, the lands like those acquired by direct purchase and without the consent of the States, remains subject to the general political jurisdiction of the States in which they are located. As property of the United States they are not, however, subject to taxation by the States.14

12 114 U. S. 525; 5 Sup. Ct. Rep. 995; 29 L. ed. 264.

13 Kohl v. United States, 91 U. S. 367; 23 L. ed. 449; St. Louis v. W. U. Tel. Co., 148 U. S. 92.

14 Van Brocklin v. Tennessee, 117 U. S. 151; 6 Sup. Ct. Rep. 670; 29 L. ed. 845.