Kenworth was founded out of the ownership of Gerlinger Motors in Portland, Oregon, (1912) by brothers George T. Gerlinger and Louis Gerlinger Jr. In 1914, they expanded their dealership into vehicle manufacturing, marketing a truck named the Gersix. The name came from its inline six-cylinder engine, one of the first trucks equipped with this. the Gersix was framed in structural steel, intended for commercial use. It soon was in high demand by loggers in the Pacific Northwest.
In 1916, Gerlinger Motors relocated from Portland to Tacoma, Washington,leasing a building from Seattle businessman Edgar K. Worthington. Gerlinger Motors filed for bankruptcy in 1917 and was placed for sale, with E.K. Worthington acquiring the company with business partner Captain Frederick Kent. The name of the company was changed to Gersix Motors to enphasize connection to truck manufacturing.