The phrase "this Union" in U.S. Const. art. IV, § 3 was and is a union of States, equal in power, dignity and authority, each competent to exert that residuum of sovereignty not delegated to the United States by the Constitution itself.
Petitioner citizens claimed that the Oklahoma Act, providing for the immediate location of the capital at Oklahoma City was void as repugnant to the Enabling Act of Congress of June 16, 1906, under which the State was admitted to the Union. Prior to the Oklahoma Act, the capital was located in another city. The citizens were owners of property interests in the former location of the capital. The state court rejected the citizens' challenges under the state constitution. On review, the Court affirmed.
Does the state of Oklahoma have the power to locate its own seat of government?
The State, by virtue of its jurisdictional sovereignty as a state, was able to determine for its own people the proper location of the local seat of government. The power to locate its own seat of government, to change the same, and to appropriate its public money therefor, are essentially state powers beyond the control of Congress.