American, Sylvester Howard Roper (1823-1896) invented a two-cylinder, steam-engine motorcycle (powered by coal) in 1867. This can be considered the first motorcycle, if you allow your description of a motorcycle to include a steam engine. Howard Roper also invented a steam engine car.Gottlieb Daimler - First Gas Engined Motorcycle
German, Gottlieb Daimler invented the first gas-engined motorcycle in 1885, which was an engine attached to a wooden bike. That marked the moment in history when the dual development of a viable gas-powered engine and the modern bicycle collided.
Gottlieb Daimler used a new engine invented by engineer, Nicolaus Otto. Otto invented the first "Four-Stroke Internal-Combustion Engine" in 1876. He called it the "Otto Cycle Engine" As soon as he completed his engine, Daimler (a former Otto employee) built it into a motorcycle.
The Harley Davidson Motorcycle
Many of the nineteenth century inventors who worked on early motorcycles often moved on to other inventions. Daimler and Roper, for example, both went on to develop automobiles.
However, inventors such as William Harley and the Davidsons brothers continued to develop motorcycles and their business competitors were other new start-up companies such as Excelsior, Indian, Pierce, Merkel, Schickel and Thor. In 1903, William Harley and his friends Arthur and Walter Davidson launched the Harley-Davidson Motor Company. The bike had a quality engine, so it could prove itself in races, however, the company planned to manufacture it as a transport vehicle. Merchant, C. H. Lange, sold the first officially distributed Harley-Davidson in Chicago.
source:about.com
