“Article I, Section 8 of the Constitution provides clear instructions about how and under what circumstances the United States government may acquire title to property located within a state:
"Congress shall have the Power …. To exercise exclusive Legislation in all Cases whatsoever, over such District (not exceeding ten Miles square) as may, by Cession of Particular States, and the Acceptance of Congress, become the Seat of the Government of the United States, and 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, dock-Yards and other needful Buildings."
This was interpreted by the first congresses to require that when any Federal installation was to be built within the boundaries of the state, the government had to purchase the property (unless it lay within the Public Domain) and the state legislature had to pass a law agreeing to the acquisition of the property. From the earliest days of the Republic, states have proved very agreeable to government installations, both from the money spent locally to build the fort or court-house, as well as the government payroll which would follow.
The process was very simple: a state would, through its members of Congress and senators, argue that the National Interest required that a fort be built, such as one in the middle of Charleston Harbor. The necessary legislation would pass Congress and be signed by the President. Then the state legislature would pass a law granting title (if the state owned the property) or affirming title (if the land was privately owned) to the United States.
---------->The one general exception was a clause inserted to allow state officials to enter the Federal property to seize fugitives from justice or to serve civil process papers.<---------
Depending upon the property in question there might also be affirmations of the right of eminent domain, i.e., if the private owner was unwilling to sell, the property would be appraised and, under the Fifth Amendment, the government would judicially take title, paying the owner the appraised price. In other cases, the state's approval was contingent upon the Federal government using the land. South Carolina's legislature was so anxious to have Fort Sumter, that it provided for the first two and left out the third exception.
It is important to note that then - and now - the government refused to accept property where there was any other restriction. The state gave up all rights it might have in the property. Otherwise Congress would refuse to appropriate the necessary funds to build the installation. The States bent over backwards to make certain they got their share - and then some - of the Federal budget, including quickly removing impediments to the government acquiring title.
And it is important to note that the title given to the United States was fee simple, with specific notice that the property was exempt from any state or local taxes.
------->Except for the qualification that the property could be entered to seize fugitives,the property passed in perpetuity to the Federal government<--------.
On November 22, 1841, all issues regarding ownership of the fort were cleared up as the Federal Government was granted title to 125 acres of harbor "land" recorded in the office of the Secretary of State of South Carolina.
And there is the source, the Secretary of the State of South Carolina, which was also indicated in my original post on ownership.
At the time of the crisis at Fort Sumter; South Carolina, the United States Government, and the Confederate States Government considered the Fort to be the Lawful property of the United States Government.
Why else would the Governor send someone to Washington to attempt to Buy the Fort?