Calder is the artist who first set sculpture in motion, replacing the heroic mass and stillness of the medium with the quietly radical proposition that a sculpture might also be a thing that balances, drifts, and changes.
Calder's path into art was conditioned by an unusual combination of inheritance and training. He grew up in a household where the practical labor of sculpture was simply visible, drawings, models, commissions, and the daily working life of two generations of working sculptors. His decision to study mechanical engineering before turning to art gave him a formation almost no other modern sculptor shared, and the engineering habits of mind, balance, leverage, structure, the behavior of materials in motion, would later become the technical vocabulary of his mature work.
His move to Paris brought him into the orbit of the European avant-garde at its most generative moment. He performed his miniature Cirque Calder, wire and found-object figures animated by hand, for an audience that came to include Joan Miró, Fernand Léger, Marcel Duchamp, Man Ray, and Jean Cocteau. His skill in shaping wire into spare, improvisational portraits earned him the nickname "king of wire" in the Paris press of the period.
The decisive turn came in 1930, when a visit to Piet Mondrian's studio left him profoundly impressed by the abstract rectangles of color tacked to the studio walls. He emerged committed to a wholly abstract, geometric idiom, but with the additional ambition, alien to Mondrian, of setting that idiom in motion. The first results were small, motorized constructions that Marcel Duchamp christened "mobiles" in 1931; the related class of static, freestanding works was later named "stabiles" by the Dada poet and sculptor Hans Arp. Calder soon abandoned the motors in favor of works animated by air currents, a refinement that opened the form to chance and continuous variation.
Over the following decades he scaled the mobile up and out, from intimate hanging works to monumental public commissions installed in plazas, airports, and museum atriums on three continents. A long sequence of retrospectives, including a major Solomon R. Guggenheim Museum presentation in 1964–65, established him as one of the indispensable figures of postwar American art.
His legacy rests both on the formal invention itself and on the institution he made possible. The Calder Foundation, established by his family in 1987, oversees an unmatched collection of his work and archives, and his sculptures remain on permanent view at the Whitney Museum of American Art, the Museum of Modern Art, the National Gallery of Art, the Peggy Guggenheim Collection, the Tate, and the Centre Pompidou, among many other institutions worldwide.