Tomorrowland in the world's 30th largest economy

It started simply enough as a bit of promised land after World War II - an expansion space out of Los Angeles.

Los Angeles firms wanting to expand began to find land cheaper, and more plentiful, over the line in Orange County. When Dr. Arnold O. Beckman of Beckman Instruments began to feel cramped in Pasadena, for example, he pulled up stakes and settled down in Fullerton.

Growing families found housing cheaper there, too, and subdivisions blossomed. Some of the affluent professionals who summered on the beaches of Newport and Laguna began to realize they could rework things a bit and spend all their time in Orange County.

And people poured westward all along, the more so after so many were exposed to southern California during military service. One of the refrains one hears - from Anaheim Mayor Don Roth, for example - is ''I was out here during the war and always wanted to come back.''

The result was an explosion: County population grew from 131,000 in 1940 to 1 .9 million in 1980. By the end of the century population is projected to be 2.6 million.

The county was recently found to be the sixth most populous county in the US, and the fifth fastest-growing.

The economic growth has been equally dramatic.

Orange County has the 30th largest economy in the world, according to the Bank of America - ahead of Portugal, Israel, Egypt, and Kuwait, among other nations.

Though Orange County is statistically still to some degree a bedroom community, with 10 percent of its income earned outside its borders, the commuters now drive both ways - into and out of the county. The economic base has swollen from firms moved in from elsewhere - many of them from Los Angeles - as well as home-grown enterprises.

Orange County has come out from the shadow of Los Angeles.

Beyond sheer numbers, the county has a place in the public eye as the home of Disneyland, of the $1 million tract house, and of the famous - or notorious - Orange County conservatism. The county contains a significant belt of high-technology industry and entrepreneurialism. And it is home of the Irvine Ranch, regarded as the largest master-planned community in the world.

As it struggles with its Siamese-twin crises of transportation and housing, Orange County may be able to offer lessons to other parts of the country struggling with problems of growth and renewal.

Besides that - despite the smog and the traffic and the shallowness of the cultural roots, there's much here that's too gorgeous not to strain a reporter's ability to be tough and hard-nosed. Even pest exterminators have shops with tasteful Spanish tile roofs. And it's hard not to enjoy the sunshine or the sound of the fragrant eucalyptus trees rustling in the late afternoon breeze. Or , on a clear day, the rich blue of the sky that meets the blue of the sea stretching toward China.

Orange County has been hit by the recession of late. But a Bank of America analysis calls attention to several indications that a ''mild recovery'' is under way: personal consumption on the upswing, defense spending continuing to flow in the county, inventories growing, and the auto and housing sectors giving signs of rebounding.

However, the bank concurs with other observers that interest rates are too high to allow a robust recovery. And unless significant headway is made against its housing and transportation problems, the county's growth will continue to be cramped.

Housing prices are so high that families earning nearly $40,000 a year are eligible for what is regarded as a special ''low income'' housing program. There have also been reports of people who can't afford houses camping out in state parks. Proposition 13 has limited local governments' ability to finance infrastructure through property taxes, and so builders are being required to put in streets and sewers and are passing the costs on to home buyers.

More than 46,000 new jobs are projected for the county in 1983, with job growth averaging 4.1 percent for the year. Unemployment should be around 6 percent, down slightly from this year and considerably under national rates. Population increase - births over deaths plus movers-in - is projected at 40,000 .

If manufacturing - high-tech and all - is down slightly, the financial and services sector is doing well.

Agriculture has shrunk to a very narrow slice of the pie indeed, but Orange County crops still had a wholesale value of a quarter-billion dollars in 1981. Nursery products and cut flowers led the field, followed by strawberries and, yes, oranges. It is possible to get a whiff of strawberries from the field along the San Diego freeway. The tractors moving along their rows of crops, with the mountain in the distance like the backdrop for a giant stage set, make a visual counterpoint to the BMWs and Toyotas heading along the freeway for the office parks of Irvine and Newport.

To spend any time in Orange County is to hear of distinctions between north and south Orange County. Northern Orange County, with 80 percent of the population, is one square-grid city running into the next. Southern Orange County didn't take off until about 15 years ago; it is largely residential, and much of it is still undeveloped - but the developed areas are home of some of the most conspicuous Orange County affluence.

Vast tracts of land under single ownership are especially typical of the southern part of Orange County. Most of the southern county is unincorporated and thus comes under direct jurisdiction of the Orange County Board of Supervisors. The result is a grand opportunity for carefully planned growth, with only one political jurisdiction and one or two landowners involved.

South county also presents a grand opportunity for development. Brandon R. Birtcher, vice-president of Birtcher Pacific, a development firm based in Laguna Niguel, certainly thinks so. He has studied south county (excluding the Newport-Irvine area) and found that commercial and industrial space under construction or projected for the year 2000 will total 52 million square feet. By comparison, he says, this is more than today's San Diego, Denver, or New Orleans.

The county is becoming an independent financial center - but it's not all the way there yet. Thomas M. Self, a Business Week veteran who is now Newport Beach-based editor of The Executive, observed, ''The missing element is investment banking and venture capital. Orange County badly needs to generate more of its own capital.''

Orange County is building an arts complex to rival the fabled Los Angeles Music Center. Originally to be called the Orange County Music Center, it's now to be called the Orange County Performing Arts Center. As one official report put it,

''From an operational standpoint, it is important that the public clearly distinguishes The Center from any other in the United States.''

With the complex finished, the only thing for which Orange County residents would still depend on Los Angeles is long-distance air travel.

Orange Countians of both parties remain largely conservative politically, but the word they most often couple with ''conservative'' is ''pragmatic.'' Strident ideology is fading from the scene, along with most of its better-known proponents.

Officials here point out the collective habit of using private initiatives to solve public problems, from coping with the Indochinese refugees to launching an arts center. The result is a voluntarism that would do the Reagan administration proud - but the bottom line may simply be that this place can afford to do privately things other places do with government funds or not at all.

Orange Countians bristle at suggestions that their home is turning into a playground for the very affluent. They insist it has a highly diversified economy, including service and manufacturing jobs - ''powder blue'' collar, as one resident put it to this correspondent. Indeed, not far from the posh Belcourt subdivision in Newport Beach, where units sell for up to $900,000, is a Ford Aerospace factory where women in smocks and polyester slacks put together the guidance systems for Sidewinder heat-seeking missiles.

It's all happened remarkably fast: ''We have built within three decades more city than the Romans built in their centuries,'' the visiting reporter is told. Young people who have never known a world without television or jet travel can nonetheless reminisce about the days of orange groves everywhere and feel like old-timers as crusty as ever rocked on a front porch.

But it's not wall-to-wall subdivisions yet. Cattle still graze on ocean-view pastureland along the Pacific Coast Highway between Newport Beach and Laguna Beach. If they were people, they probably couldn't afford to live there. Up the way is the roadside Orange Inn, which proclaims a founding date - 1931 - that is almost prehistoric by southern California standards.

What has the suddenness of development meant for Orange County?

This suddenness has led to ''communities without a history, without a substantial body of old-timers - to bushes with shallow roots,'' observes Richard Baisden, a political scientist at the University of California at Irvine.

It is unclear just what the psychic implications of that phenomenon may be, and in any case no one here seems to be thinking much about them.

What is clear is that rapid development has meant there is no great stock of old housing to give newcomers, young families, and bootstrappers an inexpensive start.

Only in the older, more northerly parts of the county - Fullerton, for example - is there the sort of older, cheaper housing that makes a good first rung up the ladder.

On the other hand, said Mr. Baisden, ''This community, because it's more recent, is more appropriate to today's needs. There are not a lot of heirlooms around here.''

Indeed not. There is a quality of shiny brightness to it all that is unfamiliar to visitors used to the soot-decorated architecture and genially peeling paint of the older half of the country. Urban renewal projects are under way in areas that would be regarded as brand new in the East.

A 10-year-old shopping center - reasonably mature by local standards - seems to have been opened only this morning.

Mirror-skinned buildings gleam under the sun like presents in the expensive department-store wrap under the Christmas tree.

Orange County, as a metropolis, lacks a single main downtown, a dominant center - although that point would be disputed by each of its cities, individually.

Anaheim has the most people (225,000), plus Disneyland, Anaheim Stadium, and the convention center. Santa Ana is the county seat. Costa Mesa, with the arts center, bids fair to become the Athens of Orange County. It also has South Coast Plaza, which started out with Middle American Sears and May Company but then won Saks Fifth Avenue and Nordstrom's and has more recently worked its way up into the haute couturem stratosphere by way of Courreges, Halston, and Yves Saint Laurent boutiques.

The Newport/Irvine area, too, is an important professional, commercial, financial, and commercial center. And the resort and leisure communities of Laguna Beach and farther south retain their cachet as well.