Extreme Cantilever (1949) is the first of the three cantilevers, a striking and unexpected new direction in Calder’s sculptural practice. It is composed of three planes of sheet metal painted black and riveted together to create a pyramidal base, from which a serrated, angular protrusion rises skyward. A long, horizontal wire extends downward from its apex, acting as a lever arm to support a white kinetic mobile element delicately suspended from its tip. The sculpture appears to defy the laws of gravity, with the slender wire seemingly too insubstantial to bear the weight of the mobile. Calder’s exploration of tensile strength and stability in Extreme Cantilever draws parallels with the cantilevers used in modern architecture, which were rapidly transforming the landscape of the postwar world. The sculpture’s serrated edges imbue it with a menacing presence, which contrasts with the fragile appearance of the mobile element that hangs tenuously in space; the mobile itself, painted a luminous white, contrasts starkly with the black stabile. As Calder said in 1943, “To me the most important thing in composition is disparity.” This juxtaposition of mass and fragility, harmony and tension, is central to Extreme Cantilever, reflecting the underlying anxieties of the interwar and postwar periods.