There was no OED prior to 1770. But if you look at the word entries I have previously supplied, you should be able to see how this works. They give a meaning and they follow it with dated usage examples. I would make you a copy of the entry for citizen, but my scanner is giving me trouble right now.
I already pointed out that the first example of the US usage tying a citizen to a state comes from 1538.
ML/NJ
I would like to see this. In Johnson's dictionary, he cites the person who used the word thusly. Perhaps OED is citing a usage traceable to Switzerland. After all, the Swiss were using the word in that manner since 1370.
I keep pointing out that no other nation in the world referred to their members as "citizens." All the rest called them "Subjects" or "Sujets" in French.
The simple fact remains, the normal manner of referring to membership in a state for that time period was "Subjects."