Alexander Calder was born in Philadelphia, Pennsylvania. His father and grandfather were sculptors. Calder went to college. He became a mechanical engineer. He learned how size and weight worked together. He experimented with size, weight, space and motion. Alexander also became a sculptor.

Calder worked with metal. At that time, metal was a new material for artists. He used large flat sheets of metal. He bent the metal so it curves and came together from different parts of the ground. He was able to make large sculptures that stayed standing even when they looked as if they should fall down.

Alexander Calder is best known for his mobiles. Mobiles are moving structures hanging in the air. They have no specific forms. The mobiles are connected with poles and wires. The sculptures will move because of built-in machines or by the wind.

Calder made other non-moving sculptures he called stabiles. He used bright clear colors, often red.

Many people liked Calder’s art. It was a new kind of sculpture that was nice to look at.