A giant blast furnace named "Dorothy Six" has become the focus here of a last-ditch community effort to stop U.S. Steel Corp. from demolishing much of its Pittsburgh-area steelmaking capacity and perhaps ending forever the dominance of steel in the Monongahela Valley.

Using a novel legal strategy and grass-roots organizing tactics, a coalition of labor union, church, academic and community activists is gaining political support for an unusual plan to have their towns take over Dorothy and other industrial facilities and operate or sell them.

The key to their strategy is the formation of a state-chartered "Steel Valley Authority" with the legal power of eminent domain -- under which governments may take private property for public purposes, usually for redevelopment or public works.

"We are making history here," said Mayor Charles Martoni of Swissvale, one of eight towns in the proposed authority.

The struggle over Dorothy is part of an uphill effort in places such as the once-thriving Mon Valley to stop the industrial decline and plant closings endemic to America's "Rust Bowl." As recently as 1980, U.S. Steel employed 25,000 steelworkers at six giant plants along the broad, winding Monongahela. Now, only 5,000 jobs remain.

The battle revolves around questions of industrial policy: Are the hulking plants in areas such as Pittsburgh no longer worth saving? Must such regions turn to "high-tech" to survive? How much time, effort and money should governments and companies spend to salvage parts of those aging industries? What happens to the communities and people affected by corporate and political decisions?

Dorothy (named for the wife of a former U.S. Steel president in accord with company custom) is crucial to steel's future. It is the largest steel furnace in the region and one of only two "hot end" furnaces -- the first step in steel production. Without her million-ton annual capacity at the Duquesne Works, employment will never significantly rebound at the five other processing plants in the Mon Valley, once the heart of American steelmaking, industry analysts said.

In May 1984, U.S. Steel shut the furnace, calling it insufficiently profitable. Last October the company announced plans to demolish it along with most of the 254-acre Duquesne Works to make an industrial park. A Save Dorothy movement quickly formed among the endangered steelworkers and their supporters. They contended that Dorothy could become profitable with new capital from private investors.

"We realized that steel could be gone forever, and we decided we'd better try to do something because nobody else was," said Jim Benn, 36, who lost his job at U.S. Steel and became a leader of the Save Dorothy movement.

The idea for a steel authority originated with the Tri-State Conference on Steel, a five-year-old coalition formed when foreign imports and slumping demand began shutting mills in Pennsylvania, Ohio and West Virginia. It staved off demolition three times, got county and city governments to fund a $150,000 study with the United Steelworkers of America (USWA) on the feasibility of saving Dorothy, and organized support for the proposed authority.

"I was born and raised here, and I have 35 years in the plant, and now I see everyone leaving," said Richard Grace, 55, president of USWA Local 1408, in an impassioned plea last month at a McKeesport City Council meeting to consider joining the new steel authority.

"We can't stand by anymore and see these plants slowly, slowly dying," Grace said. "Our heritage is here. Our roots are here. Our relatives have lived here, worked here and died here. Please. We have to save what we have."

The McKeesport council voted to join. Four towns are committed. The other four are still deliberating. The final step, a formality, will be application for the state charter.

The plan's backers say the authority would have legal power under Pennsylvania law to take over industrial plants, compensate the owners, and operate or sell them -- perhaps to employes.

Eminent domain may have to be used because U.S. Steel would rather demolish Dorothy than see a potential competitor operate her, Tri-State contends.

The Rev. Garrett Dorsey, chairman of Tri-State and pastor of a working-class Roman Catholic parish of Pittsburgh, sees "social justice" in possibly using eminent domain to take over the plant. U.S. Steel and other firms used that power in past decades to get local governments to condemn thousands of homes to make way for the mills they now want to close.

Eminent domain has been threatened, but never used, in various jurisdictions to stop plant closings, according to Tri-State counsel Staughton Lynd.

General Motors Corp. induced Detroit to use it five years ago to condemn homes in the Poletown neighborhood for the "public purpose" of building a new factory, said Lynd. Tri-State argues that saving a factory is a comparable public purpose.

Supporters of the plan contend that Dorothy, at age 21, is young by steel standards and could become profitable with an investment that is small compared with the $500 million-plus cost of building a new facility. The computer-operated furnace won U.S. Steel's "Ironmaster" award for productivity in 1983 and could exceed its production quotas again, they say.

The feasibility study on Dorothy, by Locker-Albrecht Associates of New York, was released in January and gave supporters ammunition. It concluded that with a $90 million investment, the Duquesne Works could be modernized and compete profitably with foreign steel. The study also suggested that with many older facilities ready to close in coming years, Dorothy could become a leading producer -- especially if government invests more in bridge and road repairs and other steel-dependent projects.

But U.S. Steel on April 15 announced that it had studied the USWA report and determined that it would be uneconomical to restart the furnace. "We'd hate to see people put their money and their hopes into a venture that cannot succeed," said David Roderick, chairman of the nation's biggest steel company.

U.S. Steel spokesman David Higie said the company is spending $81 million to modernize its other Mon Valley blast furnace and doesn't believe the market exists anymore for a second.

Another Pittsburgh-area community group, the Denominational Ministry Strategy, has drawn national attention with the arrests of several ministers for protests against U.S. Steel and other firms closing facilities here. DMS supporters have thrown skunk oil into churches and banks, put dead fish in safe-deposit boxes, and used other inflammatory tactics to draw attention to the problems of the unemployed.

Tri-State, which is not affiliated with DMS, has instead spent several years at door-to-door political organizing, speaking to churches and Rotary Clubs, and trying to gather support for a community-based industrial recovery plan.

The Pittsburgh Post-Gazette, in a recent editorial, said Tri-State deserved praise regardless of the outcome of the battle over Dorothy: "The people who are pressing for this action are also making a larger case for the more creative use of public resources as economic levers to this region's redevelopment. That is a significant accomplishment in itself."