ALHAMBRA, CALIF. -- Looking for the real California, the new empire of the Pacific? Take Atlantic Boulevard.

The 30-mile-long trip offers few scenic attractions. But it illuminates the once-and-future West, and particularly its capital, Los Angeles.

Where the mystique of southern California is concerned, the eastern regions of Los Angeles County might as well be on the dark side of the moon. No one talks about Alhambra or Cudahy around the pool at the Beverly Hills Hotel. Travelers heading

for Disneyland may glance at

the grimy warehouses of Commerce from the fast lane of the Santa Ana Freeway, but only an empty gas tank would make them stop.

That is too bad, for Atlantic Boulevard is a rich north-south artery for the crowded neigh- borhoods where the Californians of the next century are growing up.

Americans of Latin and Asian descent will comprise the majority in the state by the year 2030, demographers say. Here is where they start.

The color and aroma of Atlantic Boulevard, a jarring mozaic of restaurants, car lots, beauty shops, motels, banks and markets, are likely to sink deep into the consciousnesses of a whole generation.

The road's northern end is at a complex six-point intersection where the San Gabriel Valley cities of Alhambra, San Marino and South Pasadena meet. A Winchell's Donut House marks the spot.

The traveler heads south through the tidy community of

Alhambra, full of small frame houses decorated with rose bushes and orange trees. Like the other valley towns, this was once a fairly homogeneous Anglo community.

Now, it takes only a couple of blocks -- until the corner of Atlantic and Alhambra Road, to be precise -- before the new era makes itself known in the form of the Cathay Bank.

The farther south, the more apparent the change. Where Valley Boulevard crosses Atlantic, traffic backs up near the American Asian Bank, Ping On Deli and the Swiss Watch Co. -- its name carefully rendered a second time in Chinese characters.

The road passes under the San Bernardino Freeway, and the traveler is in Monterey Park, scene of one of the most rapid ethnic transformations in American history.

In the early 1960s, this was a backwater -- vacant lots, old frame houses and gas stations overlooked in the rush to develop the sparkling new suburbs of Orange County much farther east.

Frederic Hsieh, an engineer originally from Hong Kong, liked

the hills and saw a place where land was cheap and many Chi- nese Americans might like to

live.

The real estate promotion that ensued turned Monterey Park into a magnet for Asians flooding

California in the wake of loos- ened immigration laws in the late 1960s.

Today, it has the highest

concentration of Asian Americans -- 40 percent -- of any U.S. suburb and has become a dis- tinctive distillation of East and West.

Near Garvey Avenue the Tai Lai Department Store and the Hoa Binh Supermarket vie for customers. In front of one restau- rant stand racks for four differ- ent Chinese-language newspa- pers.

At the RB Furniture store on Atlantic, manager Jerry Melvin and assistant manager Eileen Cheng serve a clientele somewhat different in taste from those encountered by the chain's 48 other stores.

"For instance," said Melvin, "a lot of people here come looking for round dining-room tables, because they eat off of lazy susans. We're always short of them."

Monterey Park is 35 percent Hispanic, a substantial minority that seems submerged in the jumble of Chinese-language signs that line both sides of Atlantic. But a few more blocks south, after Atlantic Boulevard passes under the Pomona Freeway, everything changes.

This is East Los Angeles, the heart of the Hispanic-American barrio. The switch in ethnicity, and to some extent language and culture, occurs so suddenly it

almost seems as if an internation- al border has been crossed. But attitudes on both sides of the

freeway are quite American. Whether their parents were born in Kaohsiung or Guadalajara, most residents here feel cut off from the immigrants pouring in now,

20 or 30 years after their own

kin.

"They sort of look at us as

outsiders," said Rose Rivera, a longtime resident and owner of International Hair Design near Whittier Boulevard, as she described the clannish, newly arrived Mexican families filling the small houses and apartment buildings throughout the area. Rivera said she is sympathetic. She remembers "when I was the only Mexican in my class at Alhambra High."

Farther south, under the Santa Ana Freeway, and through the warehouse districts of Commerce and the little downtowns of

Maywood, Bell, Cudahy and South Gate, the new Americans from south of the border have spread. Signs advertise burritos and

hot dogs, tacos and hambur- gers.

The street's name changes from Atlantic Boulevard to Atlantic Avenue once it crosses the Long Beach Freeway, but the spread of Hispanic neighborhoods continues, pushing Los Angeles toward the day when Hispanics will be a majority.

Mostly gone from eastern Los Angeles County are the blue-collar Anglo immigrants from Europe and the American South who, according to former state Democratic Party chairwoman Elizabeth Snyder, once included a significant Ku Klux Klan chapter.

The blacks who once formed the majority in Lynwood, the suburb south of South Gate and southeast of Watts, are also moving out and finding Mexican immigrants taking their places. After the next census, demographers expect the blacks on the Los Angeles city council to find themselves as hard pressed as Anglos are now to keep their seats in the changing ethnic tide.

Narrower now, having lost some of its traffic to other streets and highways, Atlantic continues south through the black neighborhoods of North Long Beach and the Anglo residential and business districts of Long Beach, stopping two blocks short of the ocean in a forest of high-rise hotels and apartment buildings.

The best rooms of all look out toward the sea and Long Beach's famous relics of the past, the ocean liner Queen Mary and the Howard Hughes Flying Boat -- the Spruce Goose. If guests faced the opposite direction, up the length of Atlantic, they could see the future.