The Harley-Davidson Knucklehead is a classic motorcycle model produced by Harley-Davidson from 1936 to 1947. It is known for its distinctive overhead valve engine design, which was a significant innovation at the time. The Knucklehead's name comes from the unique shape of its rocker boxes, resembling a knuckle. This model played a crucial role in establishing Harley-Davidson's reputation for powerful and reliable motorcycles. The Knucklehead was available in various styles, including the EL and FL models, and it quickly became popular among riders for its performance and style. Its design features, such as the iconic teardrop fuel tank and chrome accents, contributed to its lasting appeal. Today, the Knucklehead is highly sought after by collectors and motorcycle enthusiasts.