Marvin H. Caplan, 80, a founder of Neighbors Inc., whose mission was keeping a Northwest Washington community integrated in the 1950s and 1960s to show middle-class blacks and whites they could live together, died of lung cancer Jan. 12 at his home in Washington.

In the 1950s, several Washington neighborhoods saw a reversal of what had been majority-white home ownership. Using a technique called "blockbusting," real estate brokers would exploit the fear of middle-class white residents by buying their properties below cost and reselling to blacks at a large profit.

Mr. Caplan, then a professional writer and later an AFL-CIO lobbyist and executive director of the Leadership Conference on Civil Rights, moved with his family into Manor Park in 1957. Finding a local citizens group unreceptive to removing racial restriction clauses from leases, he and about 50 other residents of both races formed Neighbors Inc. the following June to combat the racism into which those real estate speculators tapped.

Ironically, the brokers' defense was that Neighbors promoted racism by discouraging black families from moving into the area in question, roughly east of Rock Creek Park, west of Blair Road, north of Ingraham Road and south of the District line.

Neighbors Inc. fought grim -- and in its estimation misleading -- statistics about District crime, property values and education levels. Members wanted to show that integration does not necessarily mean a transition from a middle-class enclave to a slum; Mr. Caplan hoped that no matter who lived there, the local character would remain middle-class.

"Some [brokers] use unethical arguments, rumors and misrepresentation of facts, as well as blatant appeals to racial prejudice in a way to evoke fear and unrest," Mr. Caplan told The Washington Post in 1961.

A year before the newspaper quoted him, Mr. Caplan wrote an article for Atlantic Monthly about the effect on him of being pressured to sell by brokers. "Do I believe in brotherhood?" he wrote. "Do I believe we are all born free and equal? Do I believe in the sacredness of the individual? Suddenly I am pushed beyond easy platitudes into that difficult and stony place where we are forced to take a stand for our professed convictions or abandon them."

He continued: "Integration can depend upon a single person. And if I am sick of prejudice, if, as a Jew, I know in my blood and bones what it means to be stamped `Refuse' and thrown out on the garbage heap, I have no choice. I must remain."

By the early 1960s, the group grew to about 600 families and received major grants from the Eugene and Agnes E. Meyer Foundation and the Taconic Foundation of New York. The money made it possible to have an office and small staff.

Over the years, Neighbors' influence waned, Mr. Caplan wrote in his autobiography, "Farther Along: A Civil Rights Memoir," published in 1999 by Louisiana State University Press. Membership dropped to about 350 people; it did not have an office or paid staff; and it blended with other community groups as the city's population climbed to more than 60 percent black in the 1990s.

Mr. Caplan's daughter Freya Wigler said her father had "mixed feelings" about his Neighbors role. She said he believed the group did not achieve a total victory but at least "eased tensions and became a model" for other cities, such as New York and Chicago, experiencing racial antagonism as community dynamics changed.

Marvin Harold Caplan was born in West Philadelphia and graduated from Temple University. After served in a decoding unit of the Army during World War II, he moved to Richmond.

Considering himself an outsider twice-over, as a Jew and Northerner, he co-edited Southern Jewish Outlook, a pro-civil rights weekly magazine. He also helped start the Richmond chapter of the American Veterans Committee, an integrated veterans group, and picketed against segregationist policies at area department stores.

Harry Bernstein, a retired labor columnist at the Los Angeles Times who co-edited the magazine with Mr. Caplan, said in an interview, "We both wanted it to be a magazine to show Jewish people and blacks had the same kind of problems, even if it were different manifestations of it."

Bernstein said the magazine, which was loaded with society news and featured the occasional editorial on racial equality, did not garner the moral outrage for which Mr. Caplan was looking. So in 1951, Mr. Caplan moved to Washington as a correspondent for the much-larger Fairchild Publications, a New York-based company that ran trade publications.

From 1963 to 1981, Mr. Caplan was the senior lobbyist with the AFL-CIO's Industrial Union Department. In that job, he was persuaded by civil rights lawyer Joseph L. Rauh Jr. to become executive director of the Leadership Conference on Civil Rights, an umbrella group that included the traditional civil rights leadership of black, religious and labor leaders and grew under Mr. Caplan to include other minority groups and women's groups.

Among the major legislation for which Mr. Caplan lobbied behind the scenes were the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968. In the 1970s, he also pushed for Title IX, which prohibits discrimination in education, as well as renewals of the 1960s landmark laws.

As Hispanic groups joined LCCR, Mr. Caplan fought for their inclusion under the Voting Rights Act, despite the objection of those who felt that would dilute the original purpose, said Ralph G. Neas, who succeeded Mr. Caplan as executive director from 1981 to 1995 and is now on the executive committee.

"Marvin felt injustice anywhere is a threat to justice everywhere," Neas said, quoting the Rev. Martin Luther King Jr.

After he retired, Mr. Caplan was designated an honorary chairman of the leadership conference. He continued to attend meetings and wrote his autobiography.

Mr. Caplan stayed in Northwest Washington even as he saw panhandlers and crack houses start to appear. He felt it was wiser to stay and fight for a better community. Anything, he wrote in his autobiography, was better than a "leisure village," those "immaculate, synthetic communities for the elderly."

He was fluent in Yiddish and was a member of Tifereth Israel Congregation in Washington.

His first wife, Naomi Weltman, died in 1981.

Survivors include his companion of five years, Estelle Padawer of Washington; two daughters, Wigler of New York City and Dr. Annique Caplan of Cambridge, Mass.; a son, Bennett Caplan of Washington; a sister; and six grandchildren.