December 23 1947 Invention of the Transistor

1947: John Bardeen and Walter Brattain, with support from colleague William Shockley, demonstrate the transistor at Bell Laboratories in Murray Hill, New Jersey.

It's been called the most important invention of the 20th century. The transistor, aka point-contact transistor, is a semiconductor device that can amplify or switch electrical signals. It was developed to replace vacuum tubes.

Vacuum tubes were bulky, unreliable and consumed too much power. So AT&T's research-and-development arm, Bell Labs, started a project to find an alternative.

For nearly a decade before the first transistor was developed, Shockley, a physicist at Bell Labs, worked on the theory of such a device. But Shockley couldn't build a working model. His first semiconductor amplifier had a "small cylinder coated thinly with silicon, mounted close to a small, metal plate."