The family’s second generation, sons F. Otto and John, dedicated their personal time and wealth, along with the resources of the Foundation—which they renamed for seventeenth-century Quaker William Penn—and other family charitable funds, to improving the quality of life in the Philadelphia region. Their legacy includes the transformation of Independence Mall, which went from neglected area to international tourist destination. They also reinvigorated both the local and national Boys and Girls Club and United Way organizations, and supported opportunities for communities of color from Philadelphia to South Africa. Longtime supporters of the University of Pennsylvania, they renewed the Morris Arboretum and provided for the University Museum while giving generous grants to multiple departments of the University itself.

Today, the third and fourth generations of the family carry on the values and work of their forebears with personal contributions and commitments of time. The family-led William Penn Foundation plays a key role in improving the quality of life in Greater Philadelphia through support for arts and culture to organizations such as the Philadelphia Orchestra; the development of accessible and vibrant public spaces; and the protection of the Delaware River watershed. As part of its work increasing high-quality educational opportunities for economically disadvantaged students, the Foundation supports the creation of a stable, equitable, and adequate funding system providing needed resources for student success from preschool through 12th grade. And, in another Carnegie-like gesture, the Free Library of Philadelphia received the largest financial gift in its 120-year history from the William Penn Foundation to transform it into a vibrant, twenty-first-century institution. Clearly, the Haas family subscribes to Andrew Carnegie’s belief that, “to try to make the world in some way better than you found it, is to have a noble motive in life.”

Throughout his career, Richard Menschel has been known as a giver, generous with both his wealth and his time. His philanthropic support for numerous organizations has been directed personally, and through trusts and the Charina Foundation, the Horace W. Goldsmith Foundation, and subsequently, the Charina Endowment Fund.

In addition to his philanthropic work, Richard Menschel has contributed his leadership talent to numerous organizations, including the Joffrey Ballet and George Eastman Museum. An active collector of photography for almost fifty years, he established curatorial chairs in photography at The Morgan Library & Museum and Harvard Art Museums.

He has served on the boards of the Hospital for Special Surgery, The Morgan Library & Museum, and the Vera Institute of Justice, and generously supports the American Civil Liberties Union, the Harvard T. H. Chan School of Public Health, and the International Rescue Committee. He has been a partner in the Global Polio Eradication Initiative led by the Bill and Melinda Gates Foundation, and served on New York City’s Panel for Educational Policy under Mayor Michael R. Bloomberg. His wife and fellow philanthropist, Ronay Menschel, has been a leader in government and is active with numerous educational, housing, medical, and arts organizations.

Like his brother, Robert Menschel provides liberal support and leadership for an extensive and varied list of organizations, both large and small. He graduated from Syracuse University and then attended New York University Graduate School of Business. As a partner at Goldman Sachs, he founded the Institutional Department that became the model for the industry; he is currently a senior director of Goldman Sachs Group. Robert Menschel is also chairman and managing director of the foundation Vital Projects Fund, a director of the Charina Endowment Fund, and former managing director of the Horace W. Goldsmith Foundation.

Robert Menschel clearly agrees with Andrew Carnegie’s belief that “there is no mode of disposing of surplus wealth creditable to thoughtful and earnest men into whose hands it flows save by using it year by year for the general good.” His enthusiastic commitment to education and social reform, as well as health and the arts, knows no bounds. He established the Light Work Photography Organization’s program and Media Center at Syracuse University and the Menschel Photography Gallery at the Museum of Modern Art and the Metropolitan Museum of Art, among other photography programs around the nation. His foundation is also a leader in its commitment to criminal justice reform.

He has led the boards of the Museum of Modern Art and Syracuse University, and is a member of the Executive Committee of New York Presbyterian Hospital. He has served on the boards of the New York Public Library, the National Gallery of Art, the Institute for Advanced Study, Montefiore Hospital, Chess-in-the-Schools, and Congregation Emanu-El of New York City. He was also a member of President Clinton’s Committee on the Arts and the Humanities. Robert Menschel established the Paul Volcker Chair in Behavioral Economics at the Maxwell School of Citizenship at Syracuse University, and is the author of the book Markets, Mobs & Mayhem.

Beyond the medical field, Mr. Allen’s generosity is advancing other causes as well, from the environment to technology. The Allen Institute for Artificial Intelligence, for instance, has the singular focus of harnessing artificial intelligence for the common good. Mr. Allen is also working to help save the world’s oceans—strengthening surveillance of illegal fishing boats that are strip mining seas, funding research to counter ocean acidification, and educating chefs and consumers about sustainable seafood.

A signer of the Giving Pledge whose gifts already exceed $2 billion, Mr. Allen is a pragmatic but determined optimist. His unique approach to philanthropy leverages both the Paul G. Allen Family Foundation and his company, Vulcan Inc., which he named for the Roman god of fire, a radical, freethinking blacksmith who forged works that no one else—not even the gods—thought possible. Despite the complexity of his initiatives and investments, Mr. Allen sees his mission clearly: “If it has the potential to do good, then we should do it.”

More than a century ago, Andrew Carnegie said, “the day is coming when the test will be neither how a man was born nor how much wealth he possesses, nor even how much he knows, but how he has served his fellows.” Today, Paul Allen exemplifies this very ideal of knowledge, generosity, and service.

Mr. Huntsman’s business career began at an egg producer in Los Angeles (later purchased by Dow Chemical Co.), where at age 30 he led its container division. Soon he began his own small plastics packaging business, which grew to become the chemical manufacturer Huntsman Corporation, with more than 16,000 employees worldwide, in addition to 12,000 contract employees.

Considered among America’s most dedicated citizens and foremost philanthropists, Mr. Huntsman, with his wife, Karen, founded the Huntsman Cancer Institute at the University of Utah in Salt Lake City to accelerate the work of curing cancer through human genetics. Mr. Huntsman, a cancer survivor, lost both parents to the disease. Today, the Institute has leading-edge research laboratories and a state-of-the-art hospital treating cancer patients, including children and families.

Education also ranks high on the Huntsmans’ list, and they have contributed liberally to the University of Pennsylvania’s Wharton School and to Utah State University, among others. They provide scholarships for hundreds of students each year and support numerous local organizations the family feels are “most meritorious.” They have also responded to international crises. One such crisis came in 1988, when a devastating earthquake killed tens of thousands in Armenia. Mr. Huntsman stepped in to help, eventually making dozens of trips and donating more than $50 million, keeping up the assistance work ever since—rebuilding, setting up schools, and creating jobs. The Huntsman Foundation also sponsors education at Utah State University for scholars from Armenia, who are expected to return home when they finish their education.

An early signer of the Giving Pledge, Mr. Huntsman is said to keep a copy of Carnegie’s Gospel of Wealth at his desk as a reminder to live modestly and act as a trustee for the less fortunate. In a quote that could have come from Carnegie himself, Huntsman says, “You can’t call [people charitable] who wait until they die to leave money to charity in their will…. If they weren’t going to die, they wouldn’t leave a penny to anybody.”

A move into the private sector provided the means for the Jacobs’s journey into philanthropy. Dr. Jacobs founded, then sold, the satellite encryption company Linkabit. In 1985, he cofounded Qualcomm, a provider of wireless telecommunications products, shepherding its growth from start-up to Fortune 500 Company—one of Fortune’s 100 Best Companies to work for—now with over 28,000 employees worldwide.

Since relocating with her family to the San Diego area in the 1960s, New York City native Joan Jacobs has played an integral part in shaping the community through her activism and perseverance. She has focused her energies on numerous community groups, including support organizations at UCSD, the San Diego Symphony, and San Diego arts institutions, and she has been recognized for her service to the Jewish community. Joan and Irwin Jacobs are partners in philanthropy, which includes large gifts to UCSD’s engineering school and medical center, the San Diego Public Library, and the Jewish Community Foundation of San Diego. The Jacobs have given to MIT and the Salk Institute for Biological Studies, funding a professorship in genomics and in neuroscience. They also donated to the Jason and Irwin Jacobs Technion-Cornell Institute of Technology in New York City, designed to be a place for experimentation on the Cornell-Tech campus.

Dr. Jacobs has signed the Giving Pledge, but says it hasn’t really changed his strategy with regard to his money—a strategy that could have come from Andrew Carnegie himself. “There is no mode of disposing of surplus wealth creditable to thoughtful and earnest men into whose hands it flows,” Carnegie argued, “save by using it year by year for the general good.” Joan and Irwin Jacobs had already planned to give away more than half of their wealth, so signing the Giving Pledge was simply a way to encourage others to do the same.

In 1997, determined to bring more and better awareness to environmental challenges, Mr. Grantham and his wife, Hanne, cofounded the Grantham Foundation for the Protection of the Environment, into which they have poured ever-increasing shares of their personal wealth. They believe that mitigating and adapting to a changing climate will lead us to a more sustainable and prosperous future. Yet despite the complexity of the challenge, the foundation’s mission is written with the simplicity Carnegie would have admired: To protect and improve the health of the global environment.

Hanne Grantham, cochair of the foundation, shares responsibilities in setting funding priorities and grant allocations, which support major programs worldwide, among them: the Carnegie Airborne Observatory, Carnegie Institution for Science; Divecha Centre for Climate Change, Indian Institute of Science, Bangalore; Grantham Institute for Climate Change at Imperial College, London; and Grantham Research Institute on Climate Change and the Environment, London School of Economics. Support has also gone to the Environmental Defense Fund; InsideClimate News; the Nature Conservancy; Rare; World Wildlife Fund; and other groups working on clean air, forest protection, and environmental journalism. Above all, the Granthams recognize the urgency of spreading the word. “We focus on communications because we want the general public to better understand why environmental degradation poses grave risks,” their website says, “and why it is imperative that we act now.”

Thanks to his diligence, perseverance, and vision, Carlyle has thrived, and so has Mr. Rubenstein. This success has given him the opportunity to do what he’d always hoped to do—give back to the nation he credits for his success. He practices what he calls “patriotic philanthropy,” purchasing and gifting historic documents and supporting historic landmarks and national cultural institutions like presidential homes Montpelier and Monticello, the Washington Monument, and the National Zoo. He purchased the last privately owned copy of the Magna Carta and lent it to the National Archives in Washington, D.C., while other historic documents he owns—the 13th Amendment, the Constitution, the Declaration of Independence, and the Emancipation Proclamation—are on permanent loan to the U.S. government or historic sites.

Although his passion for history drives the largest share of his giving, he has also made major contributions in health, higher education, and the arts. He provided the funds for the David M. Rubenstein Center for Pancreatic Cancer Research at Memorial Sloan-Kettering and has given generously to Duke University, Harvard, Johns Hopkins, the University of Chicago, and the Institute for Advanced Study. He donated millions to expand D.C.’s John F. Kennedy Center for the Performing Arts and to renovate New York City’s Lincoln Center. He also donates his time, serving on over a dozen boards, including nearly all the recipients of his major gifts.

After decades of philanthropy, Mr. Rubenstein calls giving back “one of life’s greatest pleasures,” a sentiment he and Andrew Carnegie have in common. According to Carnegie, giving was not “beyond the reach of the humblest, for all can at least render to others.” Encouraging universal giving is one reason Mr. Rubenstein signed the Giving Pledge: “Everyone can and should give, and everyone can and should feel that their gifts may make the world a little bit better place.”

Unlike Carnegie, Mr. Feeney has always kept a low profile. He established Atlantic Philanthropies in 1982, and for years insisted that its grantmaking be done anonymously. In the mid-1980s, he quietly transferred virtually all of his assets to the foundation, which has since given billions in grants to education, health, peace, reconciliation, and human dignity—primarily for projects in Australia, Bermuda, Cuba, Northern Ireland, the Republic of Ireland, South Africa, the United States, and Viet Nam. Although he owns neither a home nor a car, Mr. Feeney makes countless large investments to meet today’s urgent challenges, such as kick-starting universities across Ireland and propelling that country’s knowledge economy, and doing the same for the United States by seeding the creation of such institutions as Cornell NYC Tech to be a global magnet for tech talent.

Atlantic Philanthropies has also made big bets in public health and health sciences, including support for facilities at the University of California, San Francisco, as well as in Viet Nam, Australia, and South Africa, that support world-class research, innovation, and improved services for vulnerable populations. The foundation’s grantmaking reaches across age groups, and racial, ethnic, and sectarian divides—transforming the lives of vulnerable children by improving health outcomes; ending needless expulsions of students from school and reforming the criminal justice system; and fostering peace and reconciliation in Northern Ireland and South Africa. All to promote equity, opportunity, and dignity. “Today’s needs are so great and varied that the intelligent philanthropic support and positive interventions can have greater value and impact today than if they are delayed when the needs are greater,” Mr. Feeney wrote. His actions prove he is a man of his word.