Alexander Calder also known as Sandy Calder, was an American sculptor and artist most famous for inventing the mobile. In addition to mobile and stabile sculpture, Alexander Calder also created paintings, lithographs, toys and tapestry and designed carpets.

Born in Lawnton, Pennsylvania. Calder came from a family of artists. His father, Alexander Stirling Calder, was a well-known sculptor who created many public installations, a majority of them located in Philadelphia. Calder’s grandfather, sculptor Alexander Milne Calder, was born in Scotland and immigrated to Philadelphia in 1868. Calder’s mother, Nanette Lederer Calder, was a professional portrait painter who studied at the Académie Julian and the Sorbonne in Paris. His older sister, Margaret “Peggy” Calder (her married name was Margaret Calder Hayes) was instrumental in the development of the UC Berkeley Art Museum.

When Calder was seven and his sister was nine, Stirling Calder contracted tuberculosis and Calder’s parents moved to a ranch in Oracle, Arizona. After Arizona, the Calder family moved to Pasadena, California. The windowed cellar of the family home became Calder’s first studio and he received his first set of tools. He used scraps of copper wire that he found in the streets to make jewelry and beads for his sister’s dolls. In 1907, Calder’s mother took him to the Tournament of Roses and he observed a four-horse-chariot race. This style of event later became the finale of Calder’s wire circus shows.

In 1910, Stirling Calder’s rehabilitation was complete and the Calder family moved back to Philadelphia, where he briefly attended the Germantown Academy, and then to Croton-on-Hudson in New York. After Croton, the Calders moved to Spuyten Duyvil to be closer to the Tenth Street Studio Building in New York, where Stirling Calder rented a studio. While living in Spuyten Duyvil, Calder attended Yonkers High. In 1912, Stirling Calder was appointed acting chief of the Department of Sculpture of the Panama Pacific International Exposition in San Francisco. He began work on sculptures for the exposition that was held in 1915. During Alexander Calder’s high school years between 1912 and 1915, the Calder family moved back and forth between New York and California.

Toward the end of this period he could graduate from Lowell High School in San Francisco in 1915. In 1915, Calder decided to study mechanical engineering after learning about the discipline from a classmate at Lowell High School. After 1919 he worked a variety of engineering jobs, including working as a hydraulics engineer and a draughtsman for the New York Edison Company, but he was not content in any of the roles. Having decided to become an artist, Calder moved to New York and enrolled at the Art Students' League. While a student, he worked for the National Police Gazette where, in 1925, one of his assignments was sketching the Ringling Brothers and Barnum and Bailey Circus. Calder became fascinated with the circus, a theme that would reappear in his later work.
In 1927, Calder returned to the United States. He designed several kinetic wooden push and pull toys for children. In 1928, Calder held his first solo show at a commercial gallery at the Weyhe Gallery in New York City. In 1934, he had his first solo museum exhibition in the United States at The Renaissance Society at the University of Chicago.

While in Paris, Calder met and became friends with a number of avant-garde artists, including Joan Miró, Jean Arp, and Marcel Duchamp. A visit to Piet Mondrian's studio in 1930 "shocked" him into embracing abstract art. By the end of 1931, he had quickly moved on to more delicate sculptures which derived their motion from the air currents in the room. From this, Calder's true "mobiles" were born. At the same time, Calder was also experimenting with self-supporting, static, abstract sculptures, dubbed "stabiles" by Arp to differentiate them from mobiles.

He returned to America in 1933 to settle in a farmhouse in Roxbury, Connecticut. He worked with Martha Graham, designing stage sets for her ballets and created a moving stage construction to accompany Eric Satie's Socrate in 1936. Calder was one of 250 sculptors who exhibited in the 3rd Sculpture International held at the Philadelphia Museum of Art in the summer of 1949. His mobile, International Mobile was the centerpiece of the exhibition and hangs in 2006 where it was placed in 1949. In the 1950s, Calder increasingly concentrated his efforts on producing monumental sculptures. Notable examples are ".125" for JFK Airport in 1957, "La Spirale" for UNESCO in Paris 1958 and "L'Homme" ("Man") for Expo '67 in Montreal. Calder's largest sculpture was "El Sol Rojo", constructed for the Olympic games in Mexico City. Calder created a sculpture called WTC Stabile (also known as The Cockeyed Propeller and Three Wings), which in 1971 was installed at the entrance of the World Trade Center's North Tower.

Calder died in 1976. He had been working on a third plane, entitled Tribute to Mexico, when he died.