There was no “official capital”.
Temporary measures were all the early Congresses could agree on.
Nobody wanted any other state to have a perceived advantage.
Of almost 200 independent countries, nearly 90% of them have as their capital city the largest city. The 21 exceptions are: (country / capital / largest city) [list=1]
[li]Australia / Canberra / Syndney[/li][li]Belize / Belmopan / Belize City[/li][li]Benin / Porto-Novo / Cotonou[/li][li]Brazil / Brasilia / Sao Paulo[/li][li]Cameroon / Yaound / Douala[/li][li]Canada / Ottawa / Toronto[/li][li]Cape Verde / Praia / Mindelo[/li][li]China / Beijing / Shanghai[/li][li]Ecuador / Quito / Guayaquil[/li][li]India / New Delhi / Calcutta[/li][li]Kuwait / Kuwait / Hawalli (a suburb of Kuwait City)[/li][li]Malawi / Lilongwe / Balntyre[/li][li]Malta / Valetta / Birkirkara[/li][li]Morocco / Rabat / Casablanca[/li][li]New Zealand / Wellington / Auckland[/li][li]Pakistan / Islamabad / Karachi[/li][li]Saudi Arabia / Riyadh / Jeddah[/li][li]Switzerland / Bern / Zurich[/li][li]Turkey / Ankara / Istanbul[/li][li]United States / Washington / New York[/li][li]Vietnam / Hanoi / Ho Chi Minh City[/li][/list=1] Source: http://www.kempf.com/~mrk/ref/stats/nations2.txt
I don’t know how old the data are, so some of these may be out of date.
Bibliophage, it’s worth noting that the majority of the few exceptions do have histories of being selected as political compromises between larger power centers (Washington, Ottawa, Bern), or as deliberate means to separate government from business centers, or to make a symbolic break with a colonial past (Brasilia, Islamabad, Ankara, and Abuja, which you did not list). Several others are there as the result of civil wars (Hanoi, Beijing). In only a few cases is the OP’s general rule otherwise inexplicable.
The District of Columbia was originally laid out as 10 x 10 miles, not 10 x 10 km.
Tokyo isn’t exactly one city. It’s basically a province, albeit it has a different name (to instead of ken) which is why Tokyo has a governor. Tokyo is divided into smaller cities (Shibuya, Roppongi, etc.) and those are divvied into what are essentially townships. Basically, Tokyo is more like New York City than it is like Washington, DC.
Seoul (correctly pronounced suh-ool, not sole) follows a similar pattern to Tokyo’s; however, it is called Seo-oul t’uk-p’yul si or The Special City of the Capital.
There are at least a few problems with the list I provided above, including Nigeria’s absence which ElvisL1ves has already noticed. There isn’t always consensus on what the largest city is (see Philippines, Sudan, and India). The updated list with changes in bold (I doubt this list is completely accurate, either.): [list=1]
[li]Australia / Canberra / Syndney[/li][li]Belize / Belmopan / Belize City[/li][li]Benin / Porto-Novo / Cotonou[/li][li]Bolivia / La Paz or Sucre / Santa Cruz or La Paz[/li][li]Brazil / Brasilia / Sao Paulo[/li][li]Cameroon / Yaound / Douala[/li][li]Canada / Ottawa / Toronto[/li][li]Cape Verde / Praia / Mindelo[/li][li]China / Beijing / Shanghai[/li][li]Ecuador / Quito / Guayaquil[/li][li]India / New Delhi / Mumbai (Bombay) or Calcutta[/li][li]Kuwait / Kuwait / Hawalli (a suburb of Kuwait City)[/li][li]Malawi / Lilongwe / Balntyre[/li][li]Malta / Valetta / Birkirkara[/li][li]Morocco / Rabat / Casablanca[/li][li]New Zealand / Wellington / Auckland[/li][li]**Nigeria / Abuja / Lagos **[/li][li]Pakistan / Islamabad / Karachi[/li][li]**Philippines / Manila / Manila or Quezon City **[/li][li]**Sudan / Khartoum / Omdurman **[/li][li]Switzerland / Bern / Zurich[/li][li]Turkey / Ankara / Istanbul[/li][li]United States / Washington / New York[/li][li]Vietnam / Hanoi / Ho Chi Minh City[/li][/list=1]
Saudi Arabia has been removed because Riyadh is the capital and the largest city.
I didn’t add countries to the list as long as the largest city is some sort of capital. (Cape Town is the largest city and legislative capital of South Africa; Abidjan is the largest city and de facto capital of Cote d’Ivoire).
What “Act of Congress” established New York City as the “official” capital of the United States as reconstituted following the ratification of the new constitution?
The capital city of the United States, from 1776 (when the country was born) to 1800 (when the seat of power moved to the newly built District of Columbia) was a mobile thing. To the extent that the “capital” is the city in which the national government maintains its central offices, many cities were so honored; to the extent that the “capital” is the city in which the permanent power base of government is established, no such animal existed until May of 1790, at which time Congress established Philadelphia as the temporary capital city for 10 years. Since this appears to be an official action by Congress (whether by legislative act or by some administrative effort is unclear), it appears clear that the “official” capital for the United States from 1790 to 1800 was Philadelphia.
Bosda Di’Chi of Tricor is invited to establish why this is incorrect through use of reference to actual individual actions of Congress (either the Congress of the Acts of Confederation or the Congress of the later Constitution).
one wag commented that Washington could have been a city of northern efficiency and southern charm, but it got mixed up and became a city of northern charm and southern efficiency…
One thing I think needs to be added is that some cities like New Delhi are suburbs of larger cities. New Dehli is part of the DEHLI greater area. DEHLI is the thrid largest Indian city.
Also DC while small in city population (around 500,000) the consolidated metro area is the 5th largest area after NYC, LA, CHI, and SF.
Note the Consolidated Metro areas of Wash DC includes Baltimore. San Jose is included in the Consolidated Metro area of SF. [strange thing if you don’t count consolidated metro areas LA is bigger than NYC but that is a different thread]
I had always heard that Johannesburg was the largest city in SA. Proving this is easier said than done, in spite of a census in 1996. It seems even more than in the US, politics has prevented widespread agreement on actual census results.
I’ll try to be a benevolent hijacker. Suffice to say that a case can be made that bibliophage is right. Local administration and demographic definitions have been in a state of flux since the ascendance of the ANC, and there have been a variety of groups adjusting the undercounts in each area.
Recent figures can be found for either the city proper or the metropolitan area of Cape Town being larger than those of Johannesburg, the reverse is not always true. However, considering the geographic size of the Cape Metropolitan Area, it is probably more appropiate to compare it to the Witwatersrand area around Johannesburg, which is considerably larger in population than the Cape.
But take heart, for if we consider that
then it seems fair to say Pretoria is part of the largest metropolitan area (I see Markxxx nodding his head), and South Africa can be left off the list again.
Do I hear a Hagenees speaking there? 
Just to clear things up entirely for those not in the know: The Hague is the administrative capital of The Netherlands, as well as the official residency of the Queen (or King, as the future case may be). Amsterdam is the geographic capital - this basically stems from the period when Amsterdam was the capital of the Republiek der Zeeven Vereenigde Neederlanden (“Republic of the Seven United Netherlands”), following the 1579 Union of Utrecht during the 80 Year War with Spain, that ended in 1648. (A brief overview on the formation of the Dutch Republic here)
In Japan, the Diet used to regularly discuss moving the central government out of Tokyo. The costs involved in having the capital in the largest city in Japan are enormous. Of course, I haven’t heard much since the economy started going down the tubes so maybe they figure the cost of moving the capital out of Tokyo would outweigh the benefits involved.
My quick take on this: capital cities are often “planned communities”. That is, they are designed from the ground up to act as a location of a central government. Washington, DC is an excellent example. Major population centers tend to form for reasons relating to geography, trade routes, and the like; New York and Chicago are good examples of these. In many countries, a capital is chosen long after cities are established, and therefore the capital city IS a major city. Mexico City (formerly Tenochtitlan), for example, has long been the most populous city in Mexico, so it was only natural that it become the capital.
Now I do understand that the question was regarding countries and not U.S. states, but I thought I would just toss in the tidbit of how there there has been some ongoing consideration in Alaska to change the capital city of Juno to Anchorage. Part of the reason is the inaccessibility to State offices and services to the greater population due to the location of Juno.
Have any other states or countries considered changing the capital to the greater populated area or is Alaska unique due to the geographical extremes?
I think you mean Juneau, Alaska and not Juno. It’s named after a person, not a god.
Another reason was that for quite some time, the capital (and political control) had been bouncing between Montreal (the first capital of the Province of Canada), Toronto, and Kingston. Putting it in any of these cities provoked endless squabbles and power plays, including one time when the Parliament in Montreal was burned down and the Governor-General attacked. Finally, fed up with all this nonsense, the Queen and various advisors decided to put it in the tiny, rough lumbering town of Ottawa, mostly because it was so in the middle of nowhere that nobody could get too upset about it. (Ottawa used to be called Bytown, but I can’t remember whether the change was before or after it was renamed.)
OMG! I swear that I knew it was Juneau! HONEST! I know Alaska inside and out, truly love the place, and have seriously considered becoming a residence. I can’t believe I wrote Juno.
Excuse #1 - I have been getting my new home PC setup and until I get back on AOL or Earthlink, I have been using Juno. Juno sucks. It is pissing me off. I hate it! I am having nightmares about it. It is all I think about. It took over my typing fingers.
Am I forgiven? 
Now I feel dumb.
Juneau is unique among state capitals in that it is completely inaccessible by road. The roads in the city do not connect to the outside world, and all access is by boat or plane. Thus, I’d imagine that this is probably the extreme case of state services being inaccessible.
Germany is one that springs to mind immediately, from Bonn to Berlin. But that’s an unusual case.
I’m certain there are others. I’ve been wracking my brain for examples from various states, to Russia, Japan, Guatemala. It’s easy to find capitals in the largest cities, and former capitals in small backwaters. But so far, in all the examples I’ve found the towns are small backwaters because they are former capitals. No, St Petersburg isn’t really a small backwater, but it was bigger than Moscow in 1917.
Of course, if we’re talking states, then Ohio is an interesting case. They decided that the capital should be the largest city, so rather than moving, they re-defined Columbus to include all of Franklin County. By any fair measurement, though (county to county, or metropolitan areas), Cleveland is still quite a bit larger.
The reason why the capital of Ohio is in Columbus in the first place is that the Northwest Ordinance, under which Ohio and several other states were admitted to the Union, specified that the state capitol should be situated within a certain distance (I’m thinking it’s 30 miles) of the geometric center of the state, so Columbus is another one of those “artificial” capitals. The other two large Ohio cities (Cleveland and Cincinatti) owe their existence primarily to their respective bodies of water.
That is exactly it, a unique geographical situation. If you have ever been to Juneau you would have seen that it is only easily accessible by the small population in that area. There are only a few ways in - plane, boat, or dogsled.
We all know that over the last few hundred years many capitals have changed due to changes in rulers, but I do imagine that very few have changed due to population only.