CHICAGO, Sept. 14 - A bomb thrown into a crowd at a Chicago labor rally 118 years ago incited such intense passions that until now, people here were unable to agree on how to memorialize the victims.

The calamity that unfolded near a cluster of produce stalls called Haymarket remains a crucial episode in American history. To this day, labor leaders and social activists revere the memory of the anarchists who were unjustly executed for the crime. Police organizations and their supporters, however, have insisted that the true martyrs were the seven officers killed in the blast.

The debate raged for an astonishingly long time. Now, as it finally appears to be fading, the victims have their memorial, an imposing semi-abstract sculpture at the site of the explosion.

"It might be a little overdue," Lois Weisberg, Chicago's commissioner of cultural affairs, said Tuesday at the dedication ceremony. "Some might say 100 years."

At the ceremony, police officers, labor leaders and city officials effusively congratulated each other, suggesting that the hatreds of the late 19th century had given way to friendship and solidarity. A handful of anarchists, however, held black flags and banners to protest what they called the misrepresentation of their heroes.

"Those men who were hanged are being presented as social democrats or liberal reformers, when in fact they dedicated their whole lives to anarchy and social revolution," said one protester, Steve Craig. "If they were here today, they'd be denouncing this project and everyone involved in it."

The memorial was paid for with a $300,000 state grant approved by the legislature. There was no substantial opposition.

"I think we're showing a new way to do monuments at historic sites," said Nathan Mason, an official of the cultural affairs department who directed the project. "You make them open rather than pressing a precise meaning on people or directing them toward a specific feeling or reaction."

"This is a problem that is going to face the people who plan the memorial at the World Trade Center site," Mr. Mason said. "The needs of family members are different from the needs of society. Trying to bring different needs together in a single memorial is going to be a very difficult task."

In the last decades of the 19th century, Chicago, like many other American cities, was in the throes of a convulsive social conflict. Huge numbers of people toiled in wretched conditions, while many factory owners considered ideas like labor organization and the eight-hour workday to be criminally subversive.

After a confrontation the previous day in which police beat workers and one person was killed, anarchists called for an outdoor rally on May 4, 1886. About 10:30 that night, as the rally was drawing to a close, police officers from a nearby station arrived and ordered the protesters to disperse. As officers and speakers were arguing, a person whose identity has never been determined threw a dynamite bomb into the police ranks. Seven officers were killed, along with at least four bystanders.

The attack set off a nationwide panic. Many people saw it as proof that foreign-born terrorists were trying to destroy American democracy. In the hysteria that followed, four of the men who either spoke at the rally or helped organize it were convicted of murder and hanged. A fifth died violently in his jail cell.

No evidence connected any of these men to the bombing, and they were posthumously pardoned. A plaque at the base of the new memorial says they were "unfairly tried."

"Over the years, the site of the Haymarket bombing has become a powerful symbol for a diverse cross-section of people, ideas and movements," the carefully worded plaque says. "Its significance touches on the issues of free speech, the right of public assembly, organized labor, the fight for the eight-hour workday, law enforcement, justice, anarchy, and the right of every human being to pursue an equitable and prosperous life."

One afternoon last week, Tim Samuelson, Chicago's official cultural historian, visited the site and gave a minute-by-minute account of the events leading up to the bombing. When he reached the climax, he tossed a candy bar on what he said was the precise trajectory of the anarchist bomb.

"This was such a powerful event that people cling to its symbolism as a model case of this kind of tragedy," Mr. Samuelson said. "I can remember that in my own lifetime, not long ago, bringing up the idea of commemorating Haymarket was impossible because it revived emotions that were too strong. It took a long time to get historical perspective, to be able to look back at Haymarket and see that it was everyone's tragedy."

Dennis Gannon, president of the Chicago Federation of Labor, said lobbying by unions was instrumental in bringing the project to fruition.

"We get people coming here from all over the world, and the first thing they want to do is visit Haymarket," Mr. Gannon said. "Haymarket represents the beginning of labor rights in this country. It's really about our most important right, which is freedom of speech, freedom to protest. If you don't have that, you're going to be oppressed."

The president of Chicago's police union, Mark Donahue, said that although police officers were often used to repress the labor movement a century ago, they are now part of it.

"We've come a long way," Mr. Donahue said. "We recognize that the people who fought for labor rights in the past gave us the protections we have today."

Because the Haymarket explosion came after a rally at which anarchists and labor organizers spoke from a wagon, city officials asked competing artists to include a wagon in their designs. The winner, Mary Brogger, a sculptor from Chicago, produced a tableau of life-sized human figures around a wagon that is in pieces. They could be either assembling it or taking it apart.

"I was pretty adamant in my own mind that it would not be useful to depict violence," Ms. Brogger said. "The violence didn't seem important, because this event was made up of much bigger ideas than one particular incident. I didn't want to make the imagery conclusive. I want to suggest the complexity of truth, but also people's responsibility for their actions and for the effect of their actions."

This is not the first monument erected to the Haymarket victims, but it is the most ambitious. Three years after the bombing, a citizens committee paid to erect a statue of a policeman at the site. Some people considered it too partial, because it suggested that only police officers were victims of the event. It was damaged three times, once when a streetcar plowed into it and twice by bombs. Each time it was repaired, and it now stands safely in the courtyard of the city's police academy.

In 1970 labor historians affixed a plaque honoring the executed anarchists to a nearby building. It was stolen a few months later.

Ms. Brogger said she was curious to see if anyone would try to attack or deface her memorial.

"When I was choosing a patina," she said, "I made sure to choose one that's easy to clean."