[1][2] After moving to Milwaukee's north side on Burleigh Avenue, he started working at the Meiselbach bicycle factory at the age of 15.

Over the next few years, Harley and his childhood friend Arthur Davidson worked on their motor-bicycle with the help of Henry Melk, who owned a machine shop in northside Milwaukee.

They later received help from Ole Evinrude, who was then building gas engines of his own design for automotive use on Milwaukee's Lake Street.

[3] Harley and Davidson built their first successful prototype in 1903, which featured a looped frame, a gasoline-powered engine, and a leather drive belt.

In his spare time, Harley took up hunting, fishing and golf, and was also noted for his affinity for sketching and wildlife photography.