In many ways, Atlantic City has always functioned as a little self-sufficient empire. After all, everything goes back to the boss. This is especially true in Nucky's case; he rules his operation like "a decadent monarch" (5.3), holding sway over every decision big and small. Of course, Nucky would say that he's only doing this for the sake of his city, but it's pretty clear that he does it for one reason alone—to gain power.
Even Hap, who the book depicts as a good-hearted dude, rules the town with an iron fist. Although this little Boardwalk Empire eventually falls (or is annexed by Donald Trump, depending on how you look at it), no one can deny the heights of power reached by the leaders of this little seaside resort town.