In 1913 more than 1.1 million people entered the United States as immigrants. Mostly, they came from unfashionable neighborhoods in southern and eastern Europe. Most of them came to New York, where most of the natives (by then expanded to include the Irish, Germans and Scandinavians) organized very few Welcome Wagons to greet the new arrivals, most of whom were Italians, Poles, Russians, Greeks, Slavs and Jews. Somehow, the nation and the newcomers managed to coexist and even eventually to prosper together.

Now, 70 years later, New York City's role as principal door and roof for America's immigrants is being filled by the city of Los Angeles. Between 1970 and 1980, while the city itself grew by some 150,000 to just under 3 million, the number of people of Hispanic origin in Los Angeles nearly doubled, from 422,000 to 816,000. Mexico is the prime, but quite far from the exclusive, source of those new Angelenos. Central and South America swell the Hispanic count.

Numbers in a census book can signal changes. But to feel those changes, I urge a trip through the 24th California state senate district, which includes downtown Los Angeles, the barrio of East Los Angeles and even south Pasadena. In the district live 588,070 people. That's more than live in any of California's 45 congressional districts, or in Cleveland or Boston. There are only 40 California state senators.

In the 24th district, state assemblyman Art Torres, 35, now in his fourth term in Sacramento, is challenging the incumbent senator, Alex Garcia, whose "legislative ineffectiveness" was recently characterized by the Los Angeles Herald Examiner as "capitol legend." To move up, Torres will have to win support from voters whose nationalities include Korean, Japanese, Chinese, Filipino, Vietnamese, Samoan, Thai, Navajo, Sioux and what must be a majority of the places now holding U.N. membership.

In the city's old Irish section, Boyle Heights, captured so superbly by John Gregory Dunne in his novel, "True Confessions," not far from a Korean Seventh-Day Adventist church, is a Shakey's Pizza, which, bowing to local consumers rather than to company policy, liberally issues green peppers atop all orders. Only blocks away, the new Japanese senior center is the old Jewish senior center. The motives that brought most of the people to this part of Los Angeles were almost surely not different from those that carried the Nixon family and young Ronald Reagan to Southern California: enlarged economic and social opportunity, a nice place to live and raise a family and, maybe, a chance to start over. Los Angeles in 1982 is alive and very interesting.

This is not to suggest that the 24th senate distric is one big street festival with ethnic food and lots of dancing. There is crime in Los Angeles, too much of it, and youth gangs with guns. Fear is not a newcomer to these older neighborhoods, nor to the elderly whom that fear too often puts under house arrest. The children are not spared. At the Second Street School, a fourth-grade girl told her assemblyman of her own upset and anger at the bullying of her friends by teen-age gangs: "I'm a person, too, Mr. Torres."

There is tension in this changing city, and unemployment, as well as abundant contemporary evidence to support Willard Huntington Wright's 1913 description of Los Angeles as swarming with "spiritualists, mediums, phrenologists, astrologists, palmists and all other breeds of esoteric windjammers." But in the last 20 years of the 20th century, Los Angeles has become the real New York. It is probably the most democratic city in the country (and possibly the most materialistic, too). But Los Angeles is the place to go if you want to see firsthand America happening again. Los Angeles is terrific.