Best known as the inventor of the mobile, Alexander Calder is considered the preeminent American sculptor of the twentieth century. Calder was fascinated by motion, which led him to develop a new art form--movable sculpture. By adding movable parts to his wire and sheet metal constructions, he gave them a life of their own, allowing them to endlessly rearrange themselves in an ever-changing pattern. Later in his career, he also created looming, standing constructions of intersecting planes of steel plate which he called stabiles. In Artists: From Michelangelo to Maya Lin, G. Aimée Ergas quotes a friend and critic of Calder who noted, "Public sculpture was a stuffed shirt's paradise until [he] came along." Calder felt the same way, and he once stated that "Above all, I feel art should be happy and not lugubrious."

Calder was born in 1898 to a family of artists. His mother...