1) William S. Harley and Walter Davidson were next-door neighbors in Milwaukee, Wisconsin, where both took jobs at a local manufacturing plant, Harley as a drafstman and Davidson a pattern maker. In late 1900, Davidson took a part-time job making job patterns with a young mechanic name Ole Evinrude, who eventually developed the outboard boat motors that would bear his name.
2) Of the four founders, only Williams S. Harley was born in the USA. The Davidson brothers were all born in Scotland.
3) Their first engines were not powerful enough to motivate a bicycle beyond 25 mph, so in 1903 Harley and Davidson developed a new single-cyclinder with a 3-inch bore and 3.5-inch stroke, displacing 25 cubic inches.
4) William A. Davidson never became a motorcyclist.
5) The reason the company was called Harley-Davidson rather than Davidson-Harley was because the Davidson brothers acknowledged that Bill Harley had come up with the original motor design.
6) From the very first V-Twin in 1909, all production Harley air-cooled twins have had a vee angle of 45 degrees.
7) In 1908 Walter C. Davidson entered a Federation of American Motorcyclists economy run in New York and won it with a calculated average of 188 mpg.
The first appearance of an official Harley-Davidson racing team was at the Dodge City 300 Mile Classic race in Kansas, in July 1914.(taken from American Rider February 2009)