In 1913, when the plant was expanded, the old Harley Davidson almost reached 13,000 units. The number was increased again during the period 1916 to 1918, to around 20,000 units. This is mainly because the United States Government ordered two-wheeled vehicles for purposes of World War I. Entering the 1920's, Harley-Davidson became the largest motorcycle manufacturer in the world, with total production of 28 189 units. To market its products, Harley-Davidson has agents in 67 countries.
In this decade, Harley Davidson introduced a number of innovations. V engine developed capacity to 74 cubic inches (about 1184 cc). Gas tank teardrop design was introduced in 1925. In 1928, Harley-Davidson equipped with front brakes started. All the achievements were quite a Harley-Davidson of capital in the face of the Great Depression, economic recession in 1933. Although the number of production units declined until 3700, Harley-Davidson is able to survive. Other bike makers who also survived were the Indians. The company later became the only competitor of Harley-Davidson until the 1950s. When depression is complete, Harley-Davidson immediately step on the gas.
They introduced the EL model with a capacity of 976 cc. This popular engine models such as the Knucklehead. With Knucklehead, Harley-Davidson rose slowly. In 1936, total production reached 9812 Harley-Davidson unit.