company was still known as Gerlinger Motor Car Works, their first two full-chassis vehicles were school buses based on the Gersix truck chassis. 1920s BU series In 1926, Kenworth developed a chassis specifically for school and transit bus operators, known as the BU. The BU model sported a wheelbase of that was expanded two more inches in 1927, and could be fitted with bodies ranging from 21 to 29 passengers. The BU model also heralded the return of the Buda six-cylinder engine, and remained the company's principal offering through 1931. The new model became so popular in the Pacific Northwest that production rose from 99 units in 1927 and 127 units in 1927, to 230 units by 1930. By that time, the predominant number of BU models produced were sent to school bus body builders and were built for use in school districts throughout the Seattle and Puget Sound area of Washington state. 1930s KHC series Kenworth continued expanding into bus production throughout the 1930s, despite the Great Depression being a major influence. To assist Kenworth's 80 factory workers - who were idled by the Depression, the company undertook a bold move by introducing a new line of buses in August 1932. Known as the KHC-22 (Kenworth - Heiser - City), the 23-passenger bus was developed by Kenworth engineers as a stock demo vehicle to help aid a glum sales picture, and to jumpstart the local economy. At a time of mild economic recovery, the KHC22 proved to be very popular and sparked a renewed interest in Kenworth buses. Major operators of the KHC-22 (later expanded to a wheelbase, 33-passenger KHC-33, in September 1933) were the Portland Railway, Light & Power Company of Portland, Oregon, and Spokane United Railways. Production of Kenworth buses continued throughout the 1930s and into the early 1940s, and during this time Kenworth was manufacturing bus chassis for body builders such as Wentworth and Irwin (later renamed Wentwin), and Heiser. Heiser, long an often chosen body for school buses bearing Kenworth chassis, would later be purchased by Pacific Car and Foundry Company in 1937. Model 870 and 871 In 1933, Kenworth also released its most popular and successful line of transit bus, a conventional styled bus based on their Model 86 heavy duty truck. Powered by a Hercules JXCM engine, the model 870 as it was known, would soon be replaced by a model 871, which