I was looking at a post from /r/de about the decreases in GDP a country would experience if their capital city were to disappear. Italy and Greece would be nothing without Rome and Athens. And England would suffer without London. The US without DC wouldn’t notice a difference.
Is there a historical reason for this? Or is it just coincidental - a common development of uncommon circumstance?
North American states and provinces often chose capital cities that were deliberately not the largest city, as that was typically a seaport—with the kind of immorality and immigrant populations that leaders of the era sometimes wanted to distance themselves from. So for both capital cities and state university locations, they often wanted to spread the (expected) prosperity around, choosing a city that was centrally located within the state, and also somewhat immune from the influence and corruption of the big seaports and mercantile cities. This often also offered the opportunity for a carefully planned city with a prominent capitol site: Madison, Lincoln, Austin. In some other cases—Tallahassee, Sacramento, Carson City, Santa Fe, Topeka—a capital was chosen in the state's early history, before other cities grew vastly larger.
In other situations, particularly with national capitals, leaders deliberately wanted a compromise that would favor neither of two strong settlements. Thus Washington as a compromise among Northern and Southern states; Canberra to favor neither New South Wales nor Victoria; and Ottawa to mollify both English and French Canada.
More can always be said, but check out this thread about New York specifically courtesy /u/discovering_nyc.