BOSTON, JUNE 23 -- South African black leader Nelson Mandela brought his triumphal U.S. tour today to this city of progressive causes and racial divisions, where he praised New England's leadership in the anti-apartheid movement and identified his own cause with the American Revolution.

His emphatic tribute to the region, especially Massachusetts, was delivered before a predominantly white crowd of about 325,000 people who stood or camped along the Esplanade on the Charles River for an afternoon of musical entertainment and his evening speech.

With spectators lounging on blankets beside coolers, watching from trees or dipping their feet and paddling canoes in the river, a casual mood similar to that of the rock concerts of the 1960s prevailed.

"It was you that supported us when very few knew of our existence, our trials and tribulations," Mandela said from a covered bandstand. "It was you who rallied around our cause when we soldiered on by ourselves. Thus, you became the conscience of American society."

Mandela specifically praised the "pioneering and leading role of Massachusetts," which anti-apartheid activists consider to be the first state that adopted comprehensive sanctions against South Africa.

The state also is home to the first U.S. college to divest from companies doing business with South Africa and home to activists who, as early as 1969, protested sales to the South African government by Polaroid Corp., based across the river in Cambridge.

"Massachusetts has won a special place in our struggle," Mandela said. "I am especially grateful to you . . . for leading the fight for democracy in South Africa."

Mandela was greeted warmly by a crowd that waved and clapped hands to the rolling beat of "Bring Back Nelson Mandela," a song recorded by South African trumpeter Hugh Masekela.

After thanking the crowd for the reception, Mandela said, "We are even more touched that it was here in Boston that your own independence movement had its birth. We lower our flags in memory of Crispus Attucks, the first victim to fall in your Revolutionary War." Attucks, a black man, was among protesters shot by British troops on Boston Common in 1770.

On the eve of his first visit to Washington, the deputy president of the African National Congress (ANC) kept his focus on the unfinished business of bringing racial equality to South Africa. He again urged continued pressure on his country's government and encouraged business investment once South Africa is free of apartheid.

Before the concert and rally under a cloudy sky, Mandela raced across the city, from a school in the black community to the elegant John F. Kennedy Memorial Library overlooking Boston Harbor.

"The struggle in South Africa has reached a critical point," Mandela said during a luncheon speech at the library. "We are fighting for the kind of freedom and democracy which is no different from that which you hold dear in this country."

Once apartheid is abolished, however, Mandela said South Africa will need "massive reconstruction" with investment from the United States and other developed nations.

"The private sector will play a vital role," Mandela said, addressing concerns that the ANC envisions nationalizing industry after achieving power. Mandela said he was "sensitive" that investors will need to feel confident in a post-apartheid South Africa.

Mandela lavished praise on his host, Sen. Edward M. Kennedy (D-Mass.) for his role in imposition of U.S. economic sanctions on South Africa in 1986. He also hailed Boston Mayor Raymond Flynn (D) and Massachusetts Gov. Michael S. Dukakis (D) for the example set by the city and state in divesting.

Mandela urged his listeners, representing more than 300 of the city's top civil rights and political leaders, to press on with sanctions. "Our people have shed rivers of blood in their quest," Mandela said. "They cannot be expected to be satisfied with piecemeal reform. Indeed, it seems impossible to reform something that is inherently evil."

Showing his deft use of humor, Mandela delighted the crowd by remarking that "right now, I consider myself an honorary Irishman."

Mandela also reviewed the decades of support from the Kennedy family for his movement, particularly the 1966 visit by the late senator Robert F. Kennedy and the 1985 tour by Sen. Edward Kennedy, his brother.

Mandela did not mention a published report that, under President John F. Kennedy, the CIA pinpointed Mandela so South African security forces could arrest him in 1962. In New York, where he began his 12-day U.S. visit, Mandela said of the issue, "Let bygones be bygones."

Asked about the report, Sen. Kennedy said he had "no knowledge" of the incident. "There is no reason for me to believe it or not to believe it," he said.

At the library, musician Stevie Wonder performed a new song that he wrote for the Mandelas called "Keep Our Love Alive."

The public centerpiece today was the mammoth rally along the river separating Boston from Cambridge. The Esplanade is the site of the city's annual Fourth of July fireworks and Boston Pops orchestra concerts.

The free gathering featured folk singer Livingston Taylor; Paul Simon; Young Nation, a Boston rap group; Ladysmith Black Mambazo, a South African group, and many others. Organizers said they hoped to raise funds by collecting pledges and selling official T-shirts.

The crowd waited patiently as Mandela's schedule yielded again to delays, and he began speaking two hours later than planned. Winnie Mandela joined her husband at the rally after her scheduled appearance at St. Paul's Cathedral was canceled because of an apparent bomb threat.

Joanne McGlynn, a high school English teacher from Concord, N.H., said she came to the rally because her students raised $1,000 last year for the Fund for a Free South Africa. "I think it's so great for the kids to have a real hero, instead of Donald Trump and Oliver North," she said.

Leroy Simpson, 40, a mechanical engineer, said that he had traveled from his home in Montego Bay in Jamaica just to see Mandela and that other Jamaicans had done the same. "I planned my vacation for this purpose," he said.

Willard R. Johnson, a political science professor at the Massachusetts Institute of Technology and president of the Boston chapter of TransAfrica, cited the successful campaign to compel Polaroid to stop selling South Africa photo equipment with which the government produced the hated passbooks that blacks then had to carry.

He also noted that Hampshire College in South Hadley, Mass., in 1976 became the first U.S. college to divest.

Mandela's first stop this morning was at Madison Park High School in Roxbury, a predominantly black neighborhood that could have been part of an independent city named for him had ballot initiatives passed in 1986 and 1988.

Mandela met privately with 300 businessmen and community leaders before entering the gym. In brief remarks, he referred to the high dropout rate in Boston and urged youngsters to stay in school. As he had done in New York, Mandela asked that economic sanctions against his country not be relaxed.