By the early Sixties, there was no mistaking it. While the process had been accelerating since the end of the Second World War, finally it could be said that the centre of gravity of contemporary art, which once had rested on Paris, had shifted to America and, specifically, to New York. Many people were responsible for this surprising land-grab, not least the artists. But one man, a dealer, had played a special part. Named Leo Castelli, he was neither brash nor larger than life. (He was 5ft4ins.) He wasn't even American.
On 21 August, Castelli, who was Italian-born, died in his sleep in his Upper East Side home, aged 91. It was not huge news even here, and probably the city will not be naming an avenue after him. (Only sports heroes, like that other Italian-American who died recently, Joe DiMaggio, get such honours these days.) But still, the New York Times opened Castelli's obituary on its front page, which seldom happens, and there were paid notices from both the Guggenheim and the Museum of Modern Art.
For Castelli was a gift to New York and was remarkable in many ways. There was his childhood and adolescence shared between Trieste and Bucharest, his fluency in five languages, his famous wit and charm, his flight, with other Jews, from Paris in 1941. With his first wife, Ileana, he finally reached New York via Marrakesh, Tangier, Algeciras, Vigo and Havana - with the English nanny of their daughter.
Some will remember him for marrying, in 1995, his third wife, Barbara Bertozzi, an Italian art critic who was young enough to be his granddaughter. Others will thank him for helping, almost inadvertently, in putting the Manhattan district of SoHo on the map by opening his West Broadway gallery there in 1971. It was an act that transformed SoHo from post-industrial dilapidation to artsy chicdom.
But what counted was Castelli's career as a dealer. He took to the profession relatively late, only opening his first gallery in 1957 when he was already 50. But within a few years he had built a stable of artists that included all the names that forced the rest of the world to take New York seriously as a force in contemporary art. The careers that Castelli nurtured were, above all others, those of Robert Rauschenberg and Jasper Johns. But there were others who came under his wing too: Warhol and Lichtenstein, Frank Stella, Robert Morris, Richard Serra, James Rosenquist, Donald Judd, Dan Flavin and Bruce Nauman.
Castelli made his name with two successive exhibitions in 1958. The first was given to Johns and the second to Rauschenberg. One of the most famous stories attached to Castelli is how he was bowled over seeing the work of Johns for the first time at an exhibition of young artists. He was especially struck by the then 27-year-old's work, Green Target. A few days later he was visiting Rauschenberg in his New York studio when Rauschenberg had to visit John's studio beneath his to collect ice for a drink. Castelli accompanied him and later recollected seeing all of Johns's work around him as if he had found the "treasures of Tutankhamun". He invited Johns to join his gallery, Johns accepted instantly.
In 1960, the reputation of the Castelli gallery was further reinforced by Stella and Cy Twombley. It was only thereafter that Castelli ignited public interest, in America and in Europe, with his Pop Art stars - Lichtenstein, Warhol, Rosenquist and Claes Oldenburg. But Castelli remained more than a purveyor only of Pop Art. Also on his roster were Minimalists and Post- Minimalists. "Leo had access to an amazing list of artists," Renato Danese, of the Danese Gallery in New York commented. "I don't know whether that many estimable artists exist today, and even if they did, to have them all under one roof would be extraordinary."
They were all there - with Castelli, rather than with any other dealer - for several reasons. He invested in them because their work was groundbreaking. He wanted anyone who he sensed might be the "next" phenomenon. Castelli never had any interest in showing the works of established artists even if doing so might have brought him greater wealth. He once said: "I don't pick painters because they seem to be good, but because they seem to be leaders of a new movement."
Castelli also understood the importance of projecting this new community of New York artists beyond America, especially into Europe. He was a gentleman, for sure, but also a consummate salesman. (When De Kooning famously jabbed: "You could give that son of a bitch two beer cans and he could sell them", Johns instantly painted two Ballantine Ale cans for Castelli, who sold them at once to a leading Pop Art collector.) And because of his own cosmopolitan origins, he knew how to work the European curators. A breakthrough for him was the award of the grand prize at the Venice Biennale to Rauschenberg in 1964.
Castelli was also famously generous with those who caught his eye, becoming the first New York dealer to offer stipends to those with potential but no immediate prospect of making significant sales. Serra once recalled becoming a beneficiary of this largesse in 1965. "It was like getting a Rockefeller grant," he said. "Leo has always been generous, supportive, intimate and friendly, a throwback to another century."
Some, indeed, saw Castelli as belonging to another time. An aesthete with impeccable manners, he seemed more aristocrat than businessman. In these days of mega-mergers and Internet auctions, the personal style used by Castelli would seem anachronistic. Before quite recently moving his business back to the Upper East Side, where he started out in 1957, Castelli would be found almost every day sitting in his SoHo gallery behind a glass wall, waiting to see who came in and who he might strike up conversation with. It was an intimacy appreciated by collectors and curators - and by the artists.
"I've been learning from exhibitions at his art gallery - and from him - for 30 years," said Nan Rosenthal, the 20th Century Curator at the National Gallery in Washington, a few years ago. "It's Leo's intelligence, and his loyalty to his artist, that makes him so extraordinary. It's not been about the business, but a passion for the art."
Thus, also, Castelli showed the same generosity even to the largest institutions. Most famously, in 1988, Castelli donated Rauschenberg's 1955 Bed to the Museum of Modern Art. He had purchased the work, without any discount, at the first Rauschenberg exhibition at his gallery in 1958. He paid $1,200, by 1988 it was worth about $10m.
In its tribute to Castelli on the pages of the New York Times, the trustees of the Guggenheim said this: "No other art dealer has had such a profound effect in shaping the direction of contemporary art. He was a consummate gentleman known for his warmth, eloquence, and generosity."