In 1907 additional factory expansion came with a second floor and later with facings and additions of Milwaukee pale yellow ("cream") brick. With the new facilities production increased to 150 motorcycles.Also in this year they began selling their motorcycles to police departments, a market that has been important to them ever since.
Production in 1905 and 1906 were all single-cylinder models with 440 cc engines. In February 1907 a prototype 45-degree V-Twin engine was displayed at the Chicago Automobile Show. Although shown and advertised, very few V-Twin models were built between 1907 and 1910. Top speed was about 60 mph . Production jumped from 450 motorcycles in 1908 to 1,149 machines in 1909.
In 1911, an improved V-Twin model was introduced.a 810cc model , the 1911 V-Twin was smaller than earlier twins, but gave better performance. After 1913 the majority of bikes produced by Harley-Davidson would be V-Twin models.
By 1913, the yellow brick factory had been demolished and on the site a new 5-story structure of reinforced concrete and red brick had been built.Production that year swelled to 16,284 machines
