Why is the Epistle to the Galatians the Only Pauline Epistle Named to a Region Rather than a City?

It is indeed odd that this epistle is not written, as most of Paul's are, to the Christians of a particular city, but to those of a whole country in Asia Minor, the metropolis of which was Ancyra. Let's go through them all - Rome, Corinth, Ephesus, Philippi, Colossae, Thessalonica and now - 'to (those of the Province of) the Galatians.'  This is extraordinarily unusual and with our knowledge of a forgotten (and certainly suppressed) Council of Ancyra during the Hadrianic period - very suspicious. The name you'd expect the epistle to have been named 'to the Ancyrans.'  So why isn't it?