The Residence Act is what set up DC as the capital- straightforward legislation that can be revised.
The Capital was NY, then Philadelphia, then DC.
Additionally- the Supreme Court never determined the Constitutionality of returning parts of the District back to Virginia. It’s an open question as to the legality of this. But a closed political question.
Edit:
This is exactly what the Constitution says about the federal district:
Everything else is in the Residence Act. Legislation. Which Congress is empowered specifically to be able to do. The only limitation is that the federal district can’t be over a certain size.
Congress says that the Federal District is only the unpopulated federal buildings and parks. Everything is is now the state of - well - Washington is already taken.
State of Kathy has a nice ring.