otorcycle racing that year and would soon dominate the sport and become known as the "Wrecking Crew". By 1915, Harley-Davidson saw the emergency need of the three-speed sliding-gear transmission.
             In 1917, one-third of all Harley-Davidsons were sent overseas to the U.S. Military to fulfill their patriotic call and to aid in the war effort. The following year, roughly half of the motorcycles produced were sold to the U.S. military. In the end, about 20,000 motorcycles were used in the war, most of them Harley-Davidsons. By this time Harley-Davidson was the biggest motorcycle factory in the world with nearly 2,000 dealerships worldwide. In 1918 Harley-Davidson was the biggest motorcycle factory in the world. V-Twin was Harley's specialty, so the company tried to defeat its only remaining rival ... Indian. However, these times were the toughest because motorcycles were becoming out of date and automobile prices began to decrease
             In 1929, there was a severe impact to Harley-Davidson and its competitors. It was the Great Depression. The Excelsior-Henderson Company stopped motorcycle production in 1931. In 1933, Harley production slumped to less than 4,000 machines, its lowest figure since 1910. One reason that Harley-Davidson survived the Great Depression is because of the family ownership of the firm. The families who owned Harley-Davidson had to roll up their sleeves, get on the job, and wait for the economy to improve. The depression gave motorcycle racing a hard time also.
             But, there was a bright side to the era. The 1930s Art Deco movement, with its fresh use of color and styling, inspired Harley-Davidson to move away from the green color schemes it had been using as its paint finishes since 1917. Harley-Davidson wasted no time building momentum out of the depression, introducing its EL model, featuring the 61 cu in. overhead valve engine, also known as the Knucklehead because of the shape of its rocker boxes. The Knuc...