In 1998, Dawn Kepler was putting on a program in the East Bay geared toward interfaith couples. She called the Jewish Outreach Institute to seek help from its founder, Egon Mayer.

Not only did Mayer offer to co-sponsor the conference, but he offered to be keynote speaker, and come on his own dime, recalled Kepler, the director of Building Jewish Bridges: Outreach to Interfaith Couples, a project of the Jewish Community Federation of the Greater East Bay.

Kepler was gratified for his support, but she was in for a shock when a few days later, she received his registration card in the mail, with a check.

“He was paying like a regular person,” she said. “I called him and said, ‘What the heck, you sent me a check,’ and he said, ‘If you don’t take money, you’ll never make it in this business. Cash the check.'”

Mayer, one of the most prominent — and, in some quarters, controversial — chroniclers of American Jewry, died Friday, Jan. 30, at his Laurel Hollow, N.Y., home after battling gall bladder cancer. He was 59.

“Not only was he brilliant, and researched things no one else took the time to look at, but he was generous with his time and everything else,” Kepler recalled.

While many of Mayer’s closest friends knew he had been ill, his death came as a shock to the wider American Jewish community, where he was considered a pioneer in advocating outreach to interfaith families and unaffiliated Jews in response to rising intermarriage rates and declining communal ties.

“His was an important voice in the Jewish community,” said Gary Tobin, a demographer and president of the Institute for Jewish and Community Research in San Francisco. “He established what over time is going to be an important institutional presence in Jewish life, which is outreach.”

Mayer’s work was especially important to the Jewish communities of California and the Bay Area, Tobin added, as the intermarriage rates here are among the highest in the country.

“His was a pioneering voice in suggesting that we had to deal with intermarriage more creatively, and that it was not necessarily a loss to the community but an opportunity. There aren’t that many demographers and sociologists of Jewish life who are saying that the Jewish community needs to invest in outreach and helping Jewish families be part of the Jewish community.”

Both Kepler and Rosanne Levitt, director of the Interfaith Connection of the Jewish Community Center of San Francisco, called Mayer their mentors. “If I ever had a problem, I called him,” said Levitt.

Mayer’s scholarly work initially focused on the fervently religious in America. In 1979 he wrote “From Suburb to Shtetl,” which examined the Brooklyn neighborhood of Borough Park and how Chassidic sects confront modern culture.

In 1985 he wrote “Love and Tradition: Marriage Between Jews and Christians,” which examined intermarriage and amplified those voices who said it would benefit the Jewish community to welcome non-Jewish spouses and their children rather than shun them.

Mayer later delved deeper into interfaith families, publishing such works as “Conversion Among the Intermarried: Choosing to Become Jewish.”

In 1990 he was among the authors of the National Jewish Population Survey, funded by the national Jewish federation system. That study became infamous for its finding that — while the overall intermarriage rate was 28 percent — about half of those Jews who had wed in the past five years had married non-Jews. The community split into those urging greater efforts to prevent intermarriage, and others who said outreach to marginal Jews — and to intermarried families — would draw them closer to the tradition.

Alexandra J. Wall, j. staff writer, contributed to this report.