One of Philly's most influential artists is born

Born on this day in Philadelphia, Alexander "Sandy" Calder (1898-1976) was the son of a successful sculptor, Alexander Stirling Calder (1870-1945), and Nanette Lederer (1866-1960), a painter. He was also grandson of Alexander Milne Calder, who created the statue of William Penn atop City Hall.

Although Calder's father and grandfather were both well-known sculptors of public monuments, Alexander initially decided on a career in mechanical engineering and received training in physics and kinetics. This knowledge provided a basis for his later experimentation with motorized devices and wind-driven mobiles.

After receiving an undergraduate degree from the Stevens Institute of Technology in Hoboken, N.J., Calder worked at a variety of jobs. In 1923, he decided to enroll in the Art Students League to become a painter. From his student beginnings as a rather conventional Ashcan school painter, Calder moved on to make sculpture in wood and then wire, and, later, to develop an abstract style.

Although considered chiefly a sculptor, he was a marvelous draftsman as well, and much of his innovation first took place in two dimensions. More significantly, Alexander Calder changed the very definition of sculpture by inventing the mobile, delicately-balanced suspended moving shaped objects. He even coined the terms "mobile" and "stabile" to describe them. Although Calder was not the first sculptor to work kinetically, no other artist did so as extensively, exploring all the potential of motion.

The lobby of Federal Reserve Bank of Philadelphia, two blocks from Independence Hall, contains Alexander Calder's White Cascade (1975), the largest indoor mobile in the world. Installed in 1976, it weighs 10 tons and is suspended from the ceiling (the building's interior court is eight stories tall). White Cascade was one of Calder's last and greatest motorized sculptures.