In the early days of our Republic county borders were always being moved as population increased and decreased. Also counties were moved from one state to another as borders were re-drawn. I don’t know the legal requirement today but it is something that has been done in the past.
I live on the Eastern Shore of Maryland. There has long been talk about becoming our own state, but it will never happen. For one thing, the liberals from the western shore are invading in droves, bringing their poisonous politics with them. And, then, of course, there are the illegal aliens. The Eastern Shore is a little slice of heaven. But, I don’t know how long it will stay that way