Secession aside South Carolina could lay claim to Fort Sumter anytime from 1836 to 1860 under this provision--

from THE RISE AND FALL OF THE CONFEDERATE GOVERNMENT by President Jefferson Davis:

"South Carolina in 1805, by legislative enactment, ceded to the United States, in Charleston Harbor and on Beaufort River, various forts and fortifications, and sites for the erection of forts, on the following conditions, viz.:"That, if the United States shall not, within three years from the passing of this act, and notification thereof by the Governor of this State to the Executive of the United States, repair the fortifications now existing thereon or build such other forts or fortifications as may be deemed most expedient by the Executive of the United States on the same, and keep a garrison or garrisons therein; in such case this grant or cession shall be void and of no effect."--("Statutes at Large of South Carolina," vol. v, p. 501.)"

I tried to find these statues online but was unable to do so.

GP