Robert Indiana, the creator of one of the most iconic and widely reproduced artworks of the 20th century, died at his home on Vinalhaven, an island off the coast of Maine, on Saturday, the New York Times reported. He was 89.

Indiana, who was born Robert Clark in New Castle, Indiana, in 1928, spent much of his childhood moving around what, decades later, would become his namesake state. After his parent’s divorce he attended and graduated from Arsenal Technical High School in Indianapolis and, following a three-year stint in the US Air Force, attended the School of the Art Institute of Chicago on the GI Bill. He graduated from SAIC in 1953 and pursued subsequent studies at the Skowhegan School of Painting and Sculpture in Maine and then in Scotland, at the University of Edinburgh and Edinburgh College of Art, before returning to the US and settling in New York City in 1954.

There, he met Ellsworth Kelly and joined him and other artists living in Coenties Slip, an inlet in  Lower Manhattan whose other inhabitants included Agnes Martin, Jack Youngerman, and James Rosenquist. The impact of life in this vibrant artists’ community on Indiana was enormous, and by the late 1950s he had developed the hard-edged painting style for which he became famous, and adopted his home state as his last name.

“Robert Indiana is definitely a ‘nom de brush,’ shall we say? However, it is the only name that I use now, and the only name that I care to use,” he told Richard Brown Baker in a 1963 Smithsonian Archives of American Art oral history interview. At that time, his career was beginning to gain momentum. He had just been included in the Museum of Modern Art’s group exhibition The Art of Assemblage in 1961; the following year, the museum acquired its first painting by Indiana, “The American Dream #1” (1961), and he had his first solo show at the Stable Gallery. (MoMA now has 28 works by Indiana in its collection.)

However, it was a different dealing with MoMA that resulted in the work that would come to define Indianas career: his iconic and bold “LOVE” with the askew “O” originated in 1962 and the following year a version of it was commissioned by the Junior Council of the Museum as a print for its 1965 holiday card. (Accompanying text pieces from the time spelling “eat,” “die,” and “err” did not catch on in the same way.)

The red, blue, and green design reached a much wider audience in 1973, when the United States Postal Service put it on a stamp. To this day more than 300 million copies of the “LOVE” stamp have been printed. Versions of the text work in various sizes and media can be found at art museums and in cities the world over, including around the corner from MoMA at the corner of Sixth Avenue and 55th Street in Manhattan, on Benjamin Franklin Parkway in Philadelphia, and for the Indianapolis Art Museum in his home state. Many more have been made without his permission, as he failed to copyright the iconic design, thereby missing out on incalculable royalties. Even the potentially lucrative USPS commission only netted him a flat fee of $1,000.

“‘LOVE’ bit me,” Indiana told NPR in 2014. “It was a marvelous idea, but it was also a terrible mistake. It became too popular; it became too popular. And there are people who don’t like popularity. It’s much better to be exclusive and remote. That’s why I’m on an island off the coast of Maine, you see.” Appropriately, his 2013 retrospective at the Whitney Museum was titled Robert Indiana: Beyond LOVE.

“There’s a new wave of critics today who are reappraising Indiana in the context of Pop art, seeing how he inflects it with the darker side of the American dream,” Barbara Haskell, the curator of the Whitney retrospective, told the Times. “The work he did in the 1960s in particular is very powerful, both dark and celebratory, with layers of autobiographical and cultural references. It’s not this superficial, optimistic, clichéd work that some people associate with his monumental sculpture.”

In recent years, Indiana became increasingly reclusive and spent most of his time on Vinalhaven. Lately he had been so hard to reach that earlier today, before news of his death was confirmed, the New York Times ran a story taking up the concerns of his friends and business associates who’d been struggling to contact him. The organization that manages the rights to some of his most famous works and runs his official website, the Morgan Art Foundation, even filed a lawsuit alleging that a caretaker and art publisher had isolated him and were taking advantage of Indiana.

Despite the indelible association of his work and specifically the LOVE series with Pop art, Indiana fought that association and considered himself more purely a hard-edge painter who had made some work in the Pop idiom.

“I like Pop and there’s going to be a certain phase of my work which will probably be closer to Pop and I would like to, shall we say?” he said in the 1963 Smithsonian interview, boasting that he was working on new designs for the penny and the US flag. “I’d like to be an artist more like Picasso than like Rothko. I don’t feel that I have to go down one straight, narrow road at all. I would like to do several different things. I want to work in graphics.”

However, as the title of his Whitney exhibition attests, Indiana’s image and identity remained very much bound up in “LOVE” and the various iterations, translations, and adaptations of it that he created, and that others created without his permission.

“‘LOVE’ is purely a skeleton of all that word has meant in all the erotic and religious aspects of the theme, and to bring it down to the actual structure of the calligraphy itself is like a skeleton,” Indiana said in a 1977 interview. “It’s reducing it to the bare bones. It was really a matter of distillation.”