Harley Davidson is an American motorcycle company founded in 1903 by William H. Harley and Arthur Davidson (helped by Arthur's brother Walter Davidson). It is one of America's and world's oldest motorcycle manufacturers which makes some of the most desirable cruiser motorcycles in various markets.

In 1901, 20-year-old William S. Harley drew up plans for a small engine with a displacement of 7.07 cubic inches (116 cc) and four-inch (102 mm) flywheels[7][8] designed for use in a regular pedal-bicycle frame. Over the next two years, he and his childhood friend Arthur Davidson worked on their motor-bicycle using the northside Milwaukee machine shop at the home of their friend Henry Melk. It was finished in 1903 with the help of Arthur's brother Walter Davidson. Upon testing their power-cycle, Harley and the Davidson brothers found it unable to climb the hills around Milwaukee without pedal assistance, and they wrote off their first motor-bicycle as a valuable learning experiment.[9]

The three began work on a new and improved machine with an engine of 24.74 cubic inches (405 cc) with 9.75 in (24.8 cm) flywheels weighing 28 lb (13 kg). Its advanced loop-frame pattern was similar to the 1903 Milwaukee Merkel motorcycle designed by Joseph Merkel, later of Flying Merkel fame. The bigger engine and loop-frame design took it out of the motorized bicycle category and marked the path to future motorcycle designs. They also received help with their bigger engine from outboard motor pioneer Ole Evinrude, who was then building gas engines of his own design for automotive use on Milwaukee's Lake Street.