In 1901 they had four engines designed and ready to be fitted to bicycle frames. In 1903 the first Harley-Davidson motorcycles were built.

The brand name become very famous and appeared in ads and articles describing the motorcycle that would become a legend.  Three motorcycles were produced between 1903 and 1904 and were sold before they were even built.  During this time Walter C. Davidson Sr. and William A. Davidson joined Arthur Davidson and William S. Harley and the Harley Davidson Motor Company was officially registered with the U.S. Trade and Company Register office on September 17th 1907.  The management positions within the company  were assigned at the registration with Walter C. Davidson as President, William A. Davidson as Vice-President and Works Manager, Arthur Davidson as Secretary and General Sales Manager, and William S. Harley to serve as Chief Engineer and Treasurer. Even though the titles were officialy assigned, each person could intervene in all sectors.

In 1904 Harley-Davidson began participated in motorcycle racing   and benefited from commercial implications of the numerous victories won by their bikes and in 1913  the company decided to establish an official racing team.  Early racers such as Ralph Hepburn and Eddie Brink put Harley on the track and won races with these machines, later Joe Petreli and Red Parkhurst. Joe Petreli first raced on an Indian motorcycle, and then made a name for himself by racing Harley-Davidson's. From 1926 untill 1931 Harley interrupted their racing and Petreli raced for the Excelsior Company, which was shut down in 1931. Petreli again raced for Harley when the company started their race teams back in 1931.  Red Parkhurst became a big winner and had a long career of motorcycle racing for Harley. Participating in motorcycle racing gave Harley an edge on research and development of their motorcycles.

Harley Davidson motorcycle became the symbol of American individualism and ended up "KING OF THE ROAD", all in 100 years.