💡 1879
Electric Lamp
U.S. Patent 223,898 · 1880
From the abstract
An electric lamp for giving light by incandescence, consisting of a filament of carbon of high resistance, made as described, and secured to metallic wires, as set forth.
Note
Filed November 4, 1879. The patent was, famously, not for the idea of an incandescent bulb (Joseph Swan and others had built earlier versions) but for the specific high-resistance carbonized-bamboo filament that made the bulb economically viable in a parallel circuit. Edison's lab tried 6,000 plant materials before settling on bamboo. The patent's actual claims are a model of how narrow language wins over broad ambition.