The inspiration for the earliest dirt bike, and arguably the first motorcycle, was designed and built by the German inventors Gottlieb Daimler and Wilhelm Maybach in Bad Cannstatt (since 1905 a city district of Stuttgart) in 1885. The first petroleum-powered vehicle, it was essentially a motorized bicycle, although the inventors called their invention the Reitwagen ("riding car"). They had not set out to create a vehicle form but to build a simple carriage for the engine, which was the focus of their endeavours.
However, if one counts two wheels with steam propulsion as being a motorcycle, then the first one may have been American. One such machine was demonstrated at fairs and circuses in the eastern US in 1867, built by Sylvester Howard Roper of Roxbury, Massachusetts. There is an existing example of a Roper machine dated 1869. It's powered by a charcoal-fired two-cylinder engine, whose connecting rods directly drive a crank on the rear wheel. This machine predates the invention of the safety bicycle by many years, so its chassis is also based on the "boneshaker" bike. In 1868, the Frenchman Louis-Guillaume Perreaux patented a similar steam-powered motorcycle, probably invented independent of Roper.
In 1894, the Hildebrand & Wolfmüller became the first motorcycle available for purchase.
1948/1949 German Imme R100
Today the Japanese manufacturers, Honda, Kawasaki, Suzuki, and Yamaha dominate the motorcycle industry, although Harley-Davidson still maintains a high degree of popularity in the United States. Recent years have also seen a resurgence in the popularity of many other brands including BMW, Triumph and Ducati, and the emergence of Victory as a second successful mass-builder of big-twin American cruisers.