The proposals I heard would keep the district but make it much smaller, creating the new state (where the majority of people live) around it; the theory being that the constitution only requires a district not to exceed a 10 mile square. See e.g. https://en.wikipedia.org/wiki/DC_Admission_Act

Wouldn't it make more sense for the adjacent states to annex the now unallocated territory rather than create a tiny 50 sq. mile state which, without the important federal buildings, has less practical sovereignty than a fairly large suburb?

VA got all of its land back with the retrocession 173 years ago. MD doesn't particularly want DC back because of internal state politics reasons.

This sounds like we're halfway done, and just need to do the other half then. If Maryland doesn't want it, perhaps another state does? Hawaii, perhaps?

Only if you're wedded to the idea that DC can't be a state for some other reason.

You're 100% the way there if you're fine with DC becoming a state.

It just beta the same question: why don't you want DC to be a state? Because it takes power away from your side?

The administrative region with the nation's capital in it gets preferential treatment, pretty much universally across countries and times. DC sort of gets the opposite treatment, though, which is good from that perspective but sort of sucks for the people living there, since they have limited autonomy. So I'd posit that DC, the territory, should have no residents besides the President himself; the only way I get that without forcing seven hundred thousand people to move is to change ownership of the land to some state that wants it.

The same reason it doesn't make sense to make Denver or Seattle a state; stripped of the important Federal buildings DC has literally nothing remarkable going on about it. States need actual land and resources and all that other stuff such that you could vaguely see them operating as an actual nation. As it is it'll just end up being bullied by all the other states

Just avoid the border gore and force Maryland to take the extra land, tax income, and voting population; it'll probably be enough to knock them up a House representative or two anyway.

So Rhode Island shouldn't be a state? Wyoming? What are your requirements for being a State? Should NY or CA be 2 states? Why not?

States aren't allowed to secede, per Lincoln, so operating as a nation is irrelevant. (Texas is special.)

The original US required every state to have access to the ocean, so Colorado and Kansas shouldn't be states.

This is a remarkable statement, because more people live in DC than in Wyoming or Vermont, and the purpose of a state is to serve its people, not its buildings or "resources".

It’s poorly worded in the comment you are replying to but “make DC residents citizens of Maryland and Virginia instead of adding a state” is a cogent argument with lots of merit.

Of course those 2 senate seats that would certainly be Democratic make this a political non-starter.

The wrinkle I see in that proposal: who selects rump-DC's electors?

That’s an interesting question, and the 23rd amendment does throw a wrench in the works. There would probably still be a small number of residents, but it’s harder to justify three electoral votes.

There are federations whose capital is part of a state or a state itself. Did this problem occur anywhere in practice?

That's an interesting question.

In doing some research to formulate an answer, it really is quite striking that the US Constitution is the first of its kind, in that it conceives of a federation of co-equal sovereign states combined under a federal sovereign state. The Federalist Papers explicitly compare the proposed model against the then-existing models of Germany (i.e., Holy Roman Empire), Poland, Switzerland, Netherlands, and then-US. Keep in mind that none of those countries retain their same government form today.

In the Federalist Papers, the Netherlands is explicitly singled out for the problem of the domination of one state (Holland) over all the others, although my understanding of their history is that the state started out that way, so it's not a problem caused by the capital being part of Holland's territory. There are other examples I can think of single-state-dominant confederations (Germany provides a few examples!), but again, I'm hard-pressed to attribute any cause of that to the actual location of the capital.

At the end of the day, I don't think it would be a problem today. However, a lot of that also derives from having 200+ years of case law and custom firmly cementing the roles of federal and constituent state in a federal republic. In 1787, when the Constitution was written, that custom and precedent doesn't exist. When you're arguing that a federal government needs its own locus of power, independent of state authority, and a lot of people fear giving it that power, giving it a territory where no state can reasonably claim to be able to exercise state authority goes a long way to letting that locus of power be truly established.