One argument against treating the District of Columbia as though it were a state is that the territory in question used to be part of two states and was made into a federal enclave for a constitutional reason. But if we really believed it to be an intolerable injustice for the residents of D.C. to be deprived of citizenship in some state, then the obvious thing to do would be to return the land that Maryland and Virginia ceded to the federal government to those states and abolish the District of Columbia entirely. Washington wouldn’t be the first city to straddle state lines or the only one in which the federal government has jurisdiction over significant assets.