It sounds like an urban legend, a far-fetched, contemporary yarn, the sort of thing conspiracy theorists believe. Even the credulous and gullible raise an eyebrow or roll the eyes when they hear the claim.
However, it appears to be true.
In a fire station in Livermore, California, a light bulb has burned since 1901-- almost continuously. Only on a couple of occasions has it been turned off, during moves. When they placed it in a socket at the new location, it lit up. Power failures have also temporarily dimmed the bulb.
The bulb bears no marks, but historians believe that the Shelby Electric Company manufactured the 4-watt item. Dennis Bernal, owner of Livermore Power and Light, donated it to the city's joint fire/police station in 1901. It has served as a garage night light, first at at the fire department hose cart house in 1901, then at the new fire station in the 1930s, and again at a station opened in 1976.
In 1972, the Ripley's Believe it or Not! Museum researched the bulb and declared it authentic-- though they have a certain history of credulity. The program On the Road with Charles Kurault profiled the enigmatic bulb around the same time. The Guinness Book of World Records has also listed the bulb, though they state only that evidence supports the town's claim. Numerous newspapers, magazines, radio and tv shows have investigated the bulb. The skeptical Mikkelsons of the Snopes Urban Legend Site vouch for the bulb's authenticity.
The Livermore light likely served as the inspiration for Byron the Immortal Light Bulb from Thomas Pynchon's Gravity's Rainbow.
Livermore celebrates its bulb, and threw a centennial for it in 2001. They also established a bulb webcam, at the official website (See http://www.centennialbulb.org/photos.htm). The bulb's incandescence can be viewed from around the world.
Livermore's bulb is not unique. A New York City hardware store had a 1912 light which continued to burn until at least the 1970s. A bulb at the Palace Theater in Fort Worth, Texas lasted 68 years. Another in the washroom of an Ipswich Electrical Shop appears to have lasted from 1930 to 2001, when it finally went the way of all flash.
Some people wonder why modern lights could not burn so long. Others expound theories conspiratorial and claim that such lights could easily be manufactured, but that the vast, all-powerful bulb-manufacturing interests prevent it from happening, lest they lose our repeat business. Steven Johnson of Lawrence Berkeley National Laboratory, among others, says that, in fact, light manufacturers merely respond to consumer demand. They "can make it very dim to last for a very long period of time, or they can make it bright... and last for 750 or a thousand hours" (quoted in Knapp). The Livermore bulb has burned for more than one hundred years, but it has not burned brightly; it could really only be used as a night light.
Provided the fire-fighters of Livermore's Station #6 are not otherwise occupied, the public may visit the bulb Monday through Friday from 8 am to 5 pm.
Don Knapp "A 96-year-old light bulb is still going." CNN Sci-Tech. http://www.cnn.com/TECH/9703/25/longest.lasting.bulb/
Livermore's Centenniel Light. http://www.centennialbulb.org/
Brian McClimans. "Bulb burns 100 years and counting." Tri-Valley Herald January 1, 2001. http://www.centennialbulb.org/newsppr2.htm
Barbara Mikkelson. "Watt a Lightbulb." Snopes Urban Legend Site. http://www.snopes.com/spoons/noose/lightbul.htm
John Miller. "Livermore's Claim to Fame." Oakland Tribune November 3, 1974.
allseeingeye says that, since the Livermore bulb is a vacuum bulb, the light could last until oxygen somehow enters it.