There is every chance that income is a multi-modal distribution, and thus one should not talk of a single median. However, the person to whom I was replying us

There is every chance that income is a multi-modal distribution, and thus one should not talk of a single median. However, the person to whom I was replying used cheap and not-so-cheerful language to suggest that it was possible to talk about this en masse. Assuming that to be reasonable, I replied with an en masse response. Certainly if you break it down at the county level, I expect you'd find multiple different patterns, and would then be faced with which ones to call "typical" or "indicative".