The American Mellons trace back to County Tyrone in Ireland, where Archibald Mellon lived before emigrating to Pennsylvania in 1816 and settling in Westmoreland County. Two years later his son Andrew and family followed, bringing the Scotch‑Irish farming line that would, within a few generations, abandon fields for finance.

The real patriarch of the dynasty is Andrew’s son Thomas Mellon, born in 1813, who grew up on that Pennsylvania farm, read Benjamin Franklin’s autobiography, and decided to trade the plough for the law and banking. As a judge turned entrepreneur in Pittsburgh he founded the bank that still bears the family name and planted the seed of a multi‑sector industrial empire.

Mellon Bank, founded in 1869, became the family’s main tool for leverage. Under Thomas’s son Andrew William Mellon, the bank and family capital took controlling or major stakes in Gulf Oil, Alcoa, Koppers, New York Shipbuilding, Carborundum and a long list of other industrial firms. Later analyses of 1930s share registers show Mellons controlling large blocks of stock in companies like Gulf, Texas Gulf Sulphur, Koppers, Virginian Railway, Brooklyn Union Gas and Pittsburgh Coal.

The list of Mellon‑linked businesses runs like a capsule history of U.S. heavy industry and infrastructure: Alcoa and Crucible Steel in metals, Monongahela and Pittsburgh Coal in energy, a chain of railroads from the Maine Central to the Delaware and Hudson, plus financial institutions like First Boston and media titles such as Newsweek and the Pittsburgh Tribune‑Review. Mellon Bank itself later merged into what is now BNY Mellon, keeping the name in the top tier of global custody and asset‑servicing finance.

Andrew William Mellon, born in 1855, became the most famous member of the family: a banker, industrialist and one of the longest‑serving U.S. Secretaries of the Treasury. Sitting in that role throughout the 1920s, he helped shape national tax policy and the financial architecture of the interwar period, all while maintaining deep private ties to the corporations his family controlled.

Andrew’s influence was not just fiscal but cultural. He assembled a vast collection of European art and old masters, then used it – along with significant funds – to create the National Gallery of Art in Washington, D.C. The Andrew Mellon Building and Andrew W. Mellon Auditorium in the capital, and the Mellon College of Science at Carnegie Mellon University in Pittsburgh, keep his name embedded in the symbolic infrastructure of the American state.

The family itself splits into four main branches: descendants of Thomas Alexander Mellon Jr., James Ross Mellon, Andrew William Mellon and Richard Beatty Mellon. The detailed family tree reads like a cross between a court circular and a corporate directory, with repeated names cycling through law, banking, industry and politics.

Prominent figures include Gulf Oil founder William Larimer Mellon Sr.; financier and general Richard King Mellon, who bankrolls Pittsburgh’s post‑war urban “Renaissance”; philanthropist and racehorse owner Paul Mellon; reclusive heiress Cordelia Scaife May, a key funder of anti‑immigration organisations; and Richard Mellon Scaife, billionaire backer of the Heritage Foundation and owner of the Tribune‑Review. On the political side, ties run to senators like Mike Monroney and John Warner via marriage, showing how Mellon money braided into U.S. legislative and security circles.

The Mellons are not just donors but institution‑builders. Beyond the National Gallery of Art, they bankroll Carnegie Mellon University, major gifts to the University of Pittsburgh, Yale, and the University of Virginia, and create the Yale Center for British Art and the Paul Mellon Centre for Studies in British Art. Their name is attached to residential colleges at Yale, gardens at the White House, and nature reserves like Beechwood Farms.

At the same time, different branches fund sharply ideological projects. Cordelia Scaife May underwrites groups like the Center for Immigration Studies, FAIR and NumbersUSA through the Colcom Foundation and related vehicles, making immigration restriction a Mellon policy domain. Richard Mellon Scaife’s foundations – Allegheny, Carthage, Sarah Scaife, Scaife Family – pour tens of millions into conservative think tanks, media outlets and watchdog groups such as the Heritage Foundation and the National Legal and Policy Center. Art museums and anti‑immigration white papers, in other words, sit on the same family balance sheet.

The family’s physical footprint stretches from Pennsylvania to Virginia and the Outer Banks. Mellon Park and Mellon Square anchor their presence in Pittsburgh; the Gulf Tower and Cathedral of Learning stand as corporate and educational monuments funded with their capital. Rural holdings include Ligonier estates like Rolling Rock and Penguin Court, and donations of land for places such as Cape Hatteras National Seashore and Sky Meadows State Park.

Paul Mellon and his wife Bunny (Rachel Lambert Mellon) add a layer of horticultural and design influence, shaping the White House Rose Garden and Jacqueline Kennedy Garden and curating Oak Spring Garden as a kind of private cultural‑botanical archive. The Mellons thus own and design not just factories and banks, but landscapes, vistas and the visual language of American prestige.

The family’s own article lists an ecosystem of close associates whose careers rose under Mellon patronage: industrialists like Arthur Vining Davis at Alcoa, financiers, railroad men, politicians, insurers and art dealers such as Joseph Duveen, who helped translate Mellon money into museum‑grade collections. Senators, corporate executives and lawyers weave through the narrative as clients, partners or protégés.

Taken together, the network map – businesses, foundations, estates, associates – shows a classic American plutocratic structure: one extended Scotch‑Irish Episcopal family from Pittsburgh using a controlling bank to buy slices of the industrial economy, converting part of the proceeds into museums and universities, and using the rest to underwrite a particular vision of politics, borders and culture. In your Dark Money atlas, the Mellons are the Pittsburgh node: a banking dynasty whose capital built both the Gulf Tower and the National Gallery of Art.