Wendell Castle has been reinventing himself for the past four decades, and his latest incarnation seems destined to be his most illustrious. The continuing evolution of his organic forms, whether in plastic, wood or metal, makes him the only major American designer practicing on the cusp of art and design—territory most notably occupied by stars like Ron Arad and Zaha Hadid, in London, and Marc Newson, in Paris.

Now 75 years old, Castle shows no signs of slowing down. His most recent pieces, debuting May 1 in a major show at Barry Friedman, in New York, include assertive silhouettes that stretch the definition of furniture to its most visually extreme: bold biomorphic shapes for seating, tables, even an eight-foot-tall lamp, all cast in stainless steel, aluminum or bronze, as well as in brilliant-colored plastic and his familiar layered wood. “Wendell’s new work represents a break from the American furniture tradition,” says the New York dealer Marc Benda, a partner with Barry Friedman in Friedman Benda. “It is innovative, mature and possibly groundbreaking.”

This should be the year Castle moves into the international spotlight. In November, he received a Lifetime Achievement Award from the Brooklyn Museum of Art and New York gallery R 20th Century has featured his vintage and reeditioned work at Design Miami/Basel since 2005. Barry Friedman took Castle’s new pierced-steel chaise, the first of a series of four in different metals, to Art Miami in December, where it was a traffic stopper (and was subsequently sold). The Seoul gallery Seomi & Tuss held a one-man show of Castle last month, and there’s more to come: another solo exhibition in October, at Carpenters Workshop, in London; a September show of his grand-scale postmodern clocks from the 1980s at the Spencer Art Museum, in Lawrence, Kansas; European exhibitions being organized by Friedman Benda; reeditions of 1970s plastic lamps; and two books, a joint publication this year from Friedman/Friedman Benda and the other due in 2009 from R 20th Century.

Evan Snyderman, co-owner of R 20th Century, goes so far as to predict that Castle will be the first living American designer to hit the million-dollar mark. “He changed the way people look at furniture,” says Snyderman, whose gallery handles Castle’s classic wood and early plastic furniture from the 1960s and ’70s, as well as reeditions of ’70s plastic designs. The vintage wood pieces in particular rarely come to market, increasing their desirability. “They are some of the most important works in design history,” says Snyderman. “People won’t let go of them.”

Chances are it will take some time for Castle’s work to achieve those magical seven figures, but his stock is rising rapidly. A 1968 plastic Molar chair that originally sold for $150, for example, now brings several thousand dollars, and the price of a recent reedition of a large 1971 plastic conference table, set to rise with each successive issue, has reached $185,000, for the seventh piece, from $35,000 for the first. “We’ve sold vintage wood pieces for upwards of $300,000,” says Snyderman.

Surprisingly, Castle never studied furniture design. “If I had, that would have been a disaster,” he explains. “Industrial design and sculpture were a perfect combination.” At the University of Kansas, he majored in art and earned a master’s degree in industrial design, but his first venture into furniture was as a graduate student in sculpture. Although he learned metal casting at school, he began working in wood, a more affordable medium, and devised a technique of making sculpture by laminating inch-thick sections of the material—first oak and walnut, then other varieties—and sculpting them into biomorphic shapes. “To me the organic form offers the most exciting possibilities. It can never be completely understood in one glance,” he says, adding that after his work with laminated-wood sculpture, “it wasn’t such a stretch to turn it into furniture.” The laminated-layer technique, more flexible than conventional methods of woodworking, allowed him to make furniture of virtually any size and shape. His first sale, to one of his professors, was a coffee table that is now in the collection of the Smithsonian’s Renwick Gallery.