After meeting with a client in Rockville last month, I drove to a Target store in Gaithersburg in search of a reasonably priced car seat for my 3-year-old granddaughter. The Target is in a sprawling complex of big-box stores, all served and surrounded by thousands of parking spaces. Clearly this is a place to find and buy, at favorable prices, almost everything needed for exurban survival, including food, fuel and entertainment.

Perhaps the only items not for sale in the complex are antiques, used books and cars, but a number of car dealerships are only a short distance away, and I suspect that antique dealers are nearby, too.

As a D.C. resident who goes to Maryland or Virginia periodically to shop for items not easily found in the city, especially at discount prices, I realized once again why America's urban population is generally declining while its exurban population is growing dramatically.

Emblematic of exurbia, the Gaithersburg complex exists because it is, above all, convenient. That convenience stems from three factors: automobile access, acres of free parking and a broad range of mass-produced, competitively priced products in one location.

The complex isn't beautiful to look at or architecturally distinguished. It could be anywhere in America, which in fact is the goal of national and international merchandising chains seeking recognizable, ubiquitous architectural branding.

Indeed, for most Americans, the fundamental appeal of exurbia has little to do with aesthetics or architecture.

The exurbs appeal because many homes are still relatively affordable, public schools are still decent, most neighborhoods are stable and safe, shopping facilities are abundant, employment decentralization is creating new job opportunities, roads are built and maintained exclusively for automobile movement, and parking is ample and always free.

According to a recent story by Washington Post staff writer D'Vera Cohn, the Census Bureau reported that a number of big cities, having gained population in the 1990s, reversed direction and have lost population since 2000. The list includes Chicago, San Francisco, Boston and Minneapolis. Baltimore and the District aren't on the list because they did not grow in the 1990s, having steadily lost population over the past 50 years.

Static or shrinking city populations are generally explained by pointing to conditions in cities that contrast sharply with exurbia: soaring home prices, often-dysfunctional public schools, distressed neighborhoods, limited shopping choices, sometimes diminishing employment opportunities, horrendous traffic and scarce or costly parking.

It looks as if living in exurbia just keeps getting more convenient. In fact, does it matter any more where you live?

Thanks to the Internet, exurbanites can sit at home and communicate with the entire world in real time, whether telecommuting, shopping, doing research, following the news, playing games, looking for companionship or just gossiping. With state-of-the-art entertainment equipment and a Netflix subscription regularly providing DVDs of recently released films, exurbanites can even avoid going to the multiplex movie theater.

If you need to drive somewhere, sitting in your car with your cell phone or BlackBerry may be as appealing as sitting in your house. Indeed, your car may rival your house in amenity and comfort with its high-tech audio system, air conditioning, make-up mirrors and cushy, fully adjustable seats.

For some exurbanites, time-consuming commutes are a respite, an escape from the hassles of family and workplace. Your car becomes a mobile refuge, a domain totally under your control, with no spouse, kids, pets or colleagues to worry about.

In light of all this, who will inhabit cities in the future?

Current demographic trends and characteristics already provide clues: the affluent who can afford urban real estate, or those too poor to escape; people happy to live in high-density housing; people who enjoy walking instead of driving and use transit for travel other than just commuting; people who regularly visit museums, galleries, theaters, cafes and restaurants; people who don't mind interacting with people different from themselves; and people who relish the aesthetic amenities of city life -- the architecture, streetscapes, public squares and urban parks -- rarely found in exurbia.

Also, as the 2004 presidential election patterns suggest, cities politically will be increasingly "blue," the exurbs increasingly "red."

At the end of Cohn's report about city population losses, she writes that, according to demographers, "population growth is not the only measure of a city's success." Cohn quotes Robert Lang, director of the Metropolitan Center at Virginia Tech: "If you promote [the city] to singles, childless couples, gays, the creative class, that's not going to grow your population, but it's going to grow your municipal budget."

Do you see where we might be headed?

In a few decades, Washington and other large cities will have fewer and fewer children to educate, perhaps eliminating the need for big, expensive, urban public school systems. Then some of those urban school buildings could be converted to other uses, such as housing a Target store selling car seats to grandparents.

Roger K. Lewis is a practicing architect and a professor of architecture at the University of Maryland.