BS. Ownership didn't magically change just because South Carolina decided to walk out. Sumter was owned by the federal government, built with federal money on land deeded to them free and clear by act of the South Carolina legislature. They had no legal claim to it. None whatsoever.
“Sumter was owned by the federal government, built with federal money on land deeded to them free and clear by act of the South Carolina legislature. They had no legal claim to it. None whatsoever.”
All lands once owned by the union are reverted once the union is no longer part of the new nation. Only someone looking to pick a fight would say otherwise. Saying otherwise doesn’t pass any commonse sense test whatsoever. What was the union to do, keep their post offices open in South Carolina as well?