[Picture: Thomas Edison's first light bulb used to demonstrate his invention at Menlo Park]
Edison did not invent the first electric light bulb, but instead invented the first commercially practical incandescent light. Several designs had already been developed by earlier inventors including the patent he purchased from Henry Woodward and Mathew Evans, Moses G. Farmer, Joseph Swan, James Bowman Lindsay, William Sawyer, Sir Humphry Davy, and Heinrich Göbel.
After many experiments with platinum and other metal filaments, Edison returned to a carbon filament. The first successful test was on October 22, 1879; and lasted 13.5 hours. Edison continued to improve this design and by November 4, 1879, filed for U.S. patent 223,898 (granted on January 27, 1880) for an electric lamp using "a carbon filament or strip coiled and connected ... to platina contact wires." Although the patent described several ways of creating the carbon filament including "cotton and linen thread, wood splints, papers coiled in various ways," it was not until several months after the patent was granted that Edison and his team discovered a carbonized bamboo filament could last over 1200 hours.
In 1878, Edison formed the Edison Electric Light Company in New York City with several financiers, including J. P. Morgan and the members of the Vanderbilt family. Edison made the first public demonstration of his incandescent light bulb on December 31, 1879, in Menlo Park. It was during this time that he said, "We will make electricity so cheap that only the rich will burn candles."