A rebirth of proportions rarely recorded in American history is building in this aged mill city.

A town widely depicted a few years ago as a blighted remnant of the Industrial Revolution, plagued by outmigration and high unemployment, has quite suddenly turned a corner.

There are still stumbling blocks on the road to recovery, and Lowell will surely never again be what it was in the decades before the Civil War: the premier industrial city of the United States. But with a little luck, it could provide a model for urban revival.

Lowell's comback formula is deceptively simple: to take each of its supposedly negative characteristics and turn them into assets.

The old textile mills, once despised as grimy relics, are now seen as the architectural gems they are. They're being recycled as apartment houses for the elderly, as museums, as sites for selected industries.

In contrast to the factory desertions Lowell suffered after the textile industry began its southward migration in the 1920s, the last 18 months have brought 30 industrial expansions. One international electronics firm has even moved its headquarters into the city.

The 5.6-mile network of stone-walled canals that lace the city and once earned Lowell the label of "the Venice of America," together with the gate-house and locks of the water system that powered the textile mills, and now being recognized as priceless assets. They form the mainstay of a proposed National Cultural Park - "an industrial Williamsburg that still breaths" - which Congress, prodded by House Speaker Thomas P. O'Neill Jr. (D-Mass.) is likely to approve in 1978.

Distinguished old buildings in downtown Lowell are being protected, refurbished and recycled; paving is being stripped off old cobblestone streets; a pedestrian mall has been constructed.

Finaly, in a city with ethnic groups - it has large numbers of Greek, of Irish, of French Canadians, with scatterings of 14 other nationality groups - the new mood is to celebrate ethnicity, not to deny it.

Much of Lowell's culutral-historical-ethnic revival is the handiwork of one committed man, educator Patrick Mogan, a charming Irishman who perceived that Lowellians were accepting negative judgements outisiders made about them and their city. Mogan's solution: To help the people of the city, from all nationalities, recognize "they had a proud and positive background," to advertise Lowell as "a living exhibit of the process and consequences of the American industrial revolution."

Mogan was preaching his gospel of ethnic pride in LOwell years before the ""Roots"craze. He got the idea for the national park in 1963 and has doggedly pursued it ever since.

But hard-headed economic planing and political strategy were supplied in the early '70s when a young Oxford-educated Bostonian, Frank Keefe, became city planning director. Working closely with a "center city committee" of government, business and labor leaders, Keefe began to scratch for every cent of state or federal aid that might be available to revive the town.

Instead of new highways and connectors, Keefe pressed for improving city streets and making them more beautiful with lighting, trees and bike paths. Free architectural services were made available to anyone who'd undertake historic preservation; the city offered to brick the sidewalk in front of any improved building.

Substantial private downtown renovation for offices, apartments, restaurants and shops ensued - perhaps not "the slickest job you've ever seen," Keefe notes, "but with a lot more legitimacy than a lot of government-sponsored urban-renewal historic preservation."

Keefe's planners proposed a downtown state park, based on the canal system. And then Democratic Gov. Michael S. Dukakis, in his first week in office, pledged several million dollars for what may well be the first urban park in the United States.

Soon afterward, Dukakis made Keefe state planing director; together they formulated - using Lowell as a model - the "Massachusetts plan" of city and town revitalization, based on heavy support for the old population centers. The plan has permitted Dukakis to become a persuasive advote with the Carter administration for a national urban policy in which states can play a central role.

There is now so much infectious enthusiasm for recycling and reinvestment in Lowell, Keefe claims, that the national park is not necessary for the city's rejuvenation. "The national park would be more in the national interest than Lowell's," Keefe argues. "This was the first industrial city in America. We honor the first industrial city in America. We honor the political revolution of the Founding Fathers. But what about the Industrial Revolution that transformed American life? It happened in Lowell, and the Lowell model was replicated across the country."

A fascinating story it is: Seeking a powerful source of water power to drive the mills of their "spindle city," Lowell's founders selected a spot where the Merrimack River, flowing southward from the New Hampshire highlands, drops 32 feet.

In 1820 there was no Lowell - only a dozen family farms and a grist mill. Then came great five-and six-story mills along the river and canal banks. The population rose to 6,000 in 1830, to 33,000 by 1850. Lowell became America's greatest textile center.

Lowell's founders had a social vision, too. In contrast to the sordid conditions in English mills, they believed an industrial community could be both healthfuland moral. New England girls were recruited to work in the mills, offered concerts and lectures, housed in company boarding houses (strick rules: in by 10 p.m.).

In 20th century eyes, the scheme looks offensively paternalistic, in its time it was utopian, a plan in which Lowell took intense pride.

After the Civil War, Lowell provided jobs for thousands of destitute immigrants. The city encapulates the history of the industrial revolution, of rapid urbanization, of immigration and ethnic diversity in America.

With exhibits, canal boats and tours, a notional park would memorialize the city's rich history. Yet the ultimate fascination of Lowell is with its people - people who suffered much, yet now through a recycling of their past can look to a brighter future.

And if that can happen in a town once viewed as an industrial graveyard, why not anywhere in America?