One big happy metropolitan area goes under the knife today. The capital, which fittingly has echoed its nation's motto, henceforth contradicts it: From one, many. 202, 703, 301, and within our lifetimes, probably more. All Washington, as Caesar said of Gaul, into three parts divided is. And every time you dial the telephone, you won't be allowed to forget it.

Ten-digit dialing is a small thing, the imposition of area codes where yesterday they were cozily unnecessary. Soon enough it will be second nature to take the extra second to punch in the extra three digits. And each time, we can take some evanescent pride in this evidence that Washington has arrived as a big city, a city too big for its God-given digits.

Back when they invented area codes a generation ago, the common refrain of innocently modern people was that they feared they would all be reduced to numbers. But now one number hardly satisfies anyone.

The children of the lonely crowd, grown up to take their places in the global village, need more than one -- one for the fax machine, one for the computer modem, one for the security system, one for the car phone, one for the pager, one for the house, one (or a dozen) for the office. Compensation for a general failure of communication? Multiply those numbers by the huge agglomeration of people who have flocked to this promised land around the capital and you begin to understand why C&P Telephone could do no other.

Washington's heft has rendered obsolete the civilized idea of a "privileged calling area," in C&P parlance, of a metropolis that transcended area codes. It was the sum of its parts. Nowhere else in the country, for all these years until today, could you dial from one area code to another without, so to speak, having to declare your geographical intentions.

As Washington spread to near suburbs and then far exurbs, the seven-digit distance from any point to any other point offered some cohesion, a common sense of place, fragile and unthought though it may have been.

No more. Now we are to be reminded every day, dozens of times, of how big the city has become. It happened in Los Angeles, when 213 begat 818; in New York City, when 212 begat 718; in Boston, when 617 begat 508; in Chicago, when 312 begat 708. It happened in London just a few months ago, when the mighty 01 became 71 or 81, depending.

For those metropolitan areas, the demarcations were if anything harsher, more upsetting than what Washington faces for the first time today -- at least for those given a brand-new area code. In Los Angeles, 818 affirmed what the San Gabriel Mountains (and everyone south of them) had proclaimed all along -- that the Valley was not really L.A. Comparably, when Brooklyn, Queens and Staten Island got their own area code, it ratified what the Hudson River, and the conceit of Manhattan, had declared by fiat -- that the other boroughs were beyond the pale (though the Bronx, perversely, remains within it).

When the outer Boston suburbs, a gerrymandered arc that sweeps from Gloucester around to Framingham and down to Cape Cod and the Islands, were severed from mother 617, everyone understood that 508 was the nouveau area code, with all the bumpkinism that implied. The very same can be said of Chicago. And of London, now known, by the number, as either Inner London or Outer London (read: Outer Space).

Washington, by contrast, has always been a tripartite city. The name, even without the appended "area," implied a great deal more than the federal enclave: the pertinent neighborly parts of Maryland and Virginia too.

The fact of a local call, millions of local calls a day across state line and mighty river, suggested a cohesion, a unity. No D.C. resident would have thought that to reach her neighbor just across Western or Eastern or Southern Avenue, the friend she could see standing at her window, she would have to make telephonic reference to Baltimore, Hagerstown and Salisbury.

No more. Every time we reach out to Touch-Tone someone nearby we will have to stop and think: D.C.? Maryland? Virginia? It won't be hard. It won't take long. It's just that we'll have to do it, assign every friend or associate or merchant a jurisdiction, a quiet mental note like race or gender or hair color, an artificial distinction in a time when metropolitan Washington could use a shot of unity.

If such an assignment of identity had meaning, it would be one thing -- if 703 people were real Virginians, with their own customs and passports, or 202 people spoke a different language. But the fact is, since all of us who don't have to dial 1 first are all still Washingtonians, the prefix doesn't mean anything. It merely inspires us to think it does, to think of ourselves and others as zones apart, and doubtless better or worse too -- like a Zip code where all the upmarket junk mail and magazines go, or another where it's devilishly hard to get a mortgage. And if the prefix elicits needless prejudices here, think what having to dial 301 or 703 will breed in outlanders, all the New Yorkers and Angelenos and Chicagoans who don't know from Virginia or Maryland, except that they're creepy alien burbs.

It may be a source of comfort that no new area codes are being whelped today. But for Maryland, the comfort is temporary. Just ahead lies the division of the state, now entirely 301, into two area codes.

Maryland's main population clusters, Baltimore and the Washington suburbs, suggest where the logical line will be drawn -- somewherebetween them. C&P Telephone acknowledges as much. The question is: Which sector will inherit the original area code? Let's put it this way: Baltimore would as soon part with 301 as with the Orioles. Prince George's and Montgomery County residents ordering new signs, stationery and business cards this week might want to keep the press runs modest.