By Caroline Preston

Robert Hildreth used to be quiet about his philanthropy. But that changed when federal immigration agents raided a leather factory in New Bedford, Mass., on a March day two years ago, arresting hundreds of illegal immigrants as they stitched clothing and equipment for American soldiers overseas.

When Mr. Hildreth — a Boston banker who made a fortune selling bonds in Latin America during the 1980s and '90s — heard reports that workers were being handcuffed and shipped to detention centers hundreds of miles from their families and lawyers who could represent them, he took action.

"I was furious at Immigration for sending these people far away," he recalls.

Mr. Hildreth paid for half the bail — generally set around $5,000 — for 42 of the people arrested in the raid. The immigrants came up with the rest.

The unusual idea attracted coverage in The Boston Globe and The Wall Street Journal and won him admiration from immigrant-rights leaders. It also propelled Mr. Hildreth, long a benefactor of nonprofit groups that educate young people, to start a charity that he hopes will apply the same model of collaboration and shared responsibility to other immigrant issues.

The Foundation for an Open America, created this past spring, supports immigrant education, advocacy, and research. Mr. Hildreth, who says the stock-market collapse swallowed some of his $80-million wealth, plans eventually to set up three funds of $5-million each. He will cover the charity's annual costs of roughly $400,000 and will give some initial money for the funds.

The rest of the money — if he can raise it — will come from private and government donors, who will in some cases match money that immigrants save for education and other causes.

"Bob is a maverick. He's the kind of funder we love to work with," says Michele Lord, executive director of Public Interest Projects, in New York, a charity that houses the National Immigrant Bond Fund Mr. Hildreth created. "He doesn't come from the business of philanthropy. He wanted to get something done and doesn't suffer fools gladly and doesn't like to get bogged down in the process."

She says that Mr. Hildreth's involvement could become even more important if the United States overhauls its immigration system and charities move from their focus on pushing for change and into providing services that help immigrants.

A Laboratory for Ideas

Housed in a two-room office overlooking Copley Square, the Foundation for an Open America will remain small. It has six staff members, including Mr. Hildreth, the executive director. He does not receive a salary.

Mr. Hildreth's mornings generally begin at his desk in the back room, where a framed copy of the Globe article naming him a "Bostonian of the Year" in 2007 hangs alongside photographs of a tree farm he owns in Uruguay.

On a typical day, he might head off to promote his bond fund on the Spanish-language variety show Sabado Gigante, or to pitch his ideas about after-school programs to education charities. He has stepped away from his business to focus full-time on charity.

Mr. Hildreth says he wants the Foundation for an Open America to become a "laboratory" for his ideas on supporting immigrants and helping them succeed. As he pursues his other philanthropic interest, education, he hopes to get charities to adopt a program he developed at an organization in Lynn, Mass., that encourages Hispanic parents to save for their children's college education by matching the money they put aside. He has already succeeded in convincing a local school district, a charter school, and several nonprofit groups to sign on.

Mr. Hildreth also supports advocacy groups pushing for changes to immigration law, and pays for research and conferences to assess the policy and economic implications of immigration. He underwrote an event on remittances at a Washington think tank, for example, and is giving time and money to a committee of nonprofit groups and politicians appointed by the Massachusetts governor to present ideas on overhauling state immigration policies and services.

He will not accept applications from charities, preferring to identify opportunities and support his own ideas.

"I'm driven crazy by ideas every day," says Mr. Hildreth, who speaks with a Boston accent and a hearty sense of humor. "Sometimes I just hold my head and wish it would stop. I've had two or three ideas so far today. I'm going to fall apart."

Disagreements and Threats

Mr. Hildreth's giving has attracted controversy. A few people posted threatening videos on YouTube after the New Bedford raid, he says. Talk-radio hosts lambasted him.

One objection raised by critics: The immigrants have less of their own money to lose, raising the likelihood that they could skip out on hearings.

That has happened twice, says Patricia Malone, coordinator of the National Immigrant Bond Fund. (A lawyer declined to provide details, citing lawyer-client privilege.)

Then there are the bigger debates about immigration's impact on the American economy and society. The recession has amplified concerns that immigrants take jobs away from Americans and reduce wages, particularly in low-income professions.

Roy Beck, president of Numbers USA, a group that seeks reduced levels of immigration, notes the high number of Americans competing for medium-wage and low-wage jobs: In August, the unemployment rate among people without a high-school degree was 15.6 percent, and it was 9.7 percent for those with a high-school education but no college course work. Efforts like Mr. Hildreth's bond fund reduce opportunities for Americans, he says.

"It is misplaced concern and misplaced money," says Mr. Beck. "He decided to stand on the side of companies that hire illegal workers, and on the side of the workers themselves, and take a stand against unemployed Americans."

Mr. Hildreth counters that immigrants add more jobs to the U.S. economy by creating additional consumers, and they help make the United States more competitive. He says the economy and demand for jobs should determine the flow of immigrants. If more countries had open borders, he says, people would move to nations based on the availability of work, as they do now in the European Union.

Actions like the raid in New Bedford hurt America's image, says Mr. Hildreth. "We're a place that people want to flee to, and China is a country that people want to flee from," he says.

Immigrant Grandfather

Mr. Hildreth grew up not far from where he lives now, in Melrose, Mass. His mother was a first-generation Irish immigrant and his father the descendant of a Puritan family who arrived in the 1600s. Both were teachers.

Mr. Hildreth says he's always had a favorable impression of immigration. The history textbooks he devoured as a child painted a romantic picture of immigrants arriving in the United States, he says. He adds: "Immigrants had to be good because my grandfather was one."

After receiving a bachelor's degree from Harvard, Mr. Hildreth tried to become a teacher but soon decided he wasn't suited for the profession. Instead he got a master's degree from the Johns Hopkins School of Advanced International Studies, then got a job at the International Monetary Fund in Bolivia.

He then went to work for Drexel Burnham Lambert, the investing firm of the disgraced bond trader Michael Milken. Later Mr. Hildreth went out on his own selling bonds. "I'm a guy who talks a lot, so I like being a salesman — I love being a salesman," he says.

It was during his time with Drexel Burnham in Los Angeles that Mr. Hildreth first made a significant gift to charity. The year was 1987, the height of hysteria about the AIDS epidemic. A priest Mr. Hildreth knew was troubled by how young men sick with the disease were being ostracized by their families and winding up homeless in Los Angeles. Mr. Hildreth donated several hundred thousand dollars to convert an old property in West Hollywood into an AIDS hospice.

"That was the first time I learned I could write a big check and not be struck dead," he says. "I had been giving maybe $100 checks to Harvard. That's a big leap."

He then returned to Boston in the 1990s, where he started supporting efforts to improve educational opportunities for Hispanic and other low-income students. He read an article in The Boston Globe about how John Silber, president of Boston University, was trying to raise money for early-childhood education in Chelsea, a suburb with a large immigrant population. Mr. Hildreth gave $1.8-million to pay for a building to house a learning center, with which he remains actively involved.

Through contacts he met in Chelsea, Mr. Hildreth started supporting the charity in Lynn, which has become key to his efforts for expanding his charity work.

But those efforts were done with little fanfare. It wasn't until the New Bedford raid that Mr. Hildreth says he discovered the power of publicizing philanthropy.

"Giving anonymously is fine if you don't want to have any impact whatsoever. But if you really want to move your cause, you must put yourself on the line, and you also constantly have to work against getting a swelled head," he says. "There is a difference between a person who wants to put his name on a building at Harvard, which is a pure act of hubris, and a person who puts his name on a cause, because that's just a headache. That's just continual, progressive work."