Kenworth Truck Company is an American truck manufacturer. Founded in 1923 as the successor to Gersix Motor Company, Kenworth specializes in production of heavy-duty (Class 8) and medium-duty (Class 5–7) commercial vehicles. Headquartered in the Seattle suburb of Kirkland, Washington, Kenworth has been a wholly owned subsidiary of PACCAR since 1945, operating alongside sister company (and marketplace rival) Peterbilt Motors. Kenworth marked several firsts in truck production; the company introduced a raised-roof sleeper cab, and the first heavy-duty truck with an aerodynamically optimized body design. The Kenworth W900 has been produced continuously since 1961, serving as one of the longest production runs of any truck in automotive history. The K100 was also released in 1961. History 1912-1923: Gerlinger Motors Kenworth traces its roots to the 1912 founding of Gerlinger Motors in Portland, Oregon; the company was a car and truck dealership owned by brothers George T. Gerlinger and Louis Gerlinger, Jr. In 1914, the brothers expanded into vehicle manufacturing, marketing a truck named the Gersix. Deriving its name from its inline six-cylinder engine (one of the first trucks equipped with the type), the Gersix was framed in structural steel, intended for commercial use. While the first vehicle was completed largely as a side project, the heavy-duty construction of the Gersix found itself in demand by loggers in the Northwest. In 1916, Gerlinger Motors relocated from Portland to Tacoma, Washington, leasing a building from Seattle businessman Edgar K. Worthington. In 1917, Gerlinger Motors filed for bankruptcy and was put up for sale, with E.K. Worthington acquiring the company with business partner Captain Frederick Kent. To emphasize its connection to truck manufacturing, the company was renamed Gersix Motor Company. In 1919, Captain Kent retired, with his son Harry Kent replacing him as partner in the company. In 1922, Gersix produced 53 trucks in its final year located at its factory on Fairview Avenue at Valley Street. Following continued strong demand of the model line, the company found itself with $60,000 to reincorporate and relocate its headquarters. 1923-1930s: Kenworth Motor Truck Company In January 1923, Gersix Motor Company was reincorporated as the Kenworth Motor Truck Company, combining the names of partners Kent and Worthington. Under the new name, the company relocated within Seattle to 506 Mercer Street, and later to 1263 Mercer Street. In contrast to car manufacturers, Kenworth abstained from assembly lines, instead constructing vehicles in individual bays. The company also introduced