The Centennial Light was originally a 30-watt or 60-watt bulb but is now very dim, emitting about the same light as a 4-watt nightlight. The hand-blown, carbon-filament common light bulb was manufactured in Shelby, Ohio, by the Shelby Electric Company in the late 1890s; many just like it still exist and can be found functioning. According to Zylpha Bernal Beck, the bulb was donated to the Fire Department by her father, Dennis Bernal, in 1901. Bernal owned the Livermore Power and Water Company and donated the bulb to the fire station when he sold the company. That story has been supported by firefighter volunteers of that era.
Evidence suggests that the bulb has hung in at least four locations. It was originally hung in 1901 in a hose cart house on L Street, then moved to a garage in downtown Livermore used by the fire and police departments. When the fire department consolidated, it was moved again to a newly constructed City Hall that housed the unified departments.
Its unusual longevity was first noticed in 1972 by reporter Mike Dunstan. After weeks of interviewing people who had lived in Livermore all their lives, he wrote "Light Bulb May Be World's Oldest", published in the Tri-Valley Herald. Dunstan contacted the Guinness Book of World Records, Ripley's Believe It or Not, and General Electric, who all confirmed it as the longest-lasting bulb known in existence. The article came to the attention of Charles Kuralt of the CBS-TV program On the Road with Charles Kuralt.
According to wikipedia