Northernmost Major Cities

Which approach is more sensible likely depends entirely on how people perceive a given city. For example, by strict "city proper" population, Indianapolis is a "bigger" city than Boston. But, at least in terms of how Americans perceive cities, nobody really considers Indianapolis a "bigger" city than Boston, because there are several other "cities"--Brookline, Somerville, and Cambridge especially--that meld pretty seamlessly into Boston. There's no gap between the proper Boston city limits and those places. They all use the same subway system. You could cross from one city line to the other and to the next and never notice you had entered and then left Boston. If you're asking about who's the mayor and which police to call, the borders matter. But in the sense that most people perceive cities--where are all the people and where are the arts, economy, history, etc., Somerville, Cambridge, and Brookline are all just part of "Boston."