Headquartered in the Seattle suburb of Kirkland, Washington, Kenworth has been a wholly owned subsidiary of PACCAR since 1945,[2] operating alongside sister company (and marketplace rival) Peterbilt Motors.

[4] Deriving its name from its inline six-cylinder engine (one of the first trucks equipped with the type[4]), the Gersix was framed in structural steel, intended for commercial use.

[5] 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.

[5] In 1922, Gersix produced 53 trucks in its final year located at its factory on Fairview Avenue at Valley Street.

[6] Following continued strong demand of the model line, the company found itself with $60,000 to reincorporate and relocate its headquarters.

[8] In total, the company would supply the Army with 1,930 wreckers by the end of World War II; to accommodate the extensive increase in production, Kenworth introduced an assembly line to produce the vehicle.

[12] By 1950, Kenworth had grown outside the Pacific Northwest, marketing vehicles across the western half of the United States and across nearly 30 countries worldwide.

[11] The same year, the 900-series was introduced with an all-new "drop-frame" chassis,[11] with the CSE cabover replaced by the K-series COE (derived from the 900 series).

[11] For 1961 production, Kenworth underwent a substantial revision of its commercial truck line, debuting the W900 and the K900 (later renamed the K100); the W and K model prefixes are derived from company founders Worthington and Kent.

[16] To meet increased demand for the new product lines, Kenworth opened a new assembly facility in Kansas City, Missouri, in 1964.

[17] In 1969 Kenworth hired Gary Ridgway, who worked in their paint department for the next 32 years, during which time he murdered 48 women as the "Green River Killer"[18] During the 1970s, the company underwent further expansion, adding an all-new facility in Chillicothe, Ohio, in 1974.

While visually distinguished by the adoption of rectangular headlamps, the updates were centered around upgrading fuel economy, road handling, and reliability.

[17] Intended as an expansion of the Kenworth model line, the success of the T600 would lead to the introductions of similar designs from multiple American truck manufacturers.

In 2000, Kenworth redesigned its medium-duty COE range, with the K300 replacing the MAN-sourced design with a DAF 45 (Leyland Roadrunner) cab.

Developed primarily for off-highway applications, the K500 combined the chassis of the heavy-duty C500 and the COE cab of the DAF XF; all examples produced from 2006 to 2020 were sold for export.

[28] Australian built Kenworth models are also exported to nearby RHD markets in New Zealand, Japan, Thailand and Papua New Guinea.

[citation needed] The Kenworth "Legend" Series is a limited production truck based on a previous models styling with modern improvements such as safety and environmental.

Bus production was a mainstay at Kenworth during the early years of company history; at one time, buses were its most lucrative form of business.

When the company was still known as Gerlinger Motor Car Works, their first two full-chassis vehicles were school buses based on the Gersix truck chassis.

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.

Heiser, long an often chosen body for school buses bearing Kenworth chassis, would later be purchased by Pacific Car and Foundry Company in 1937.

[citation needed] Kenworth changed its production line early in 1939, reflecting a desire to remain "in tune" with market forces.

[citation needed] Producing about 40 buses yearly, Kenworth became a low-volume bus manufacturer, accommodating special-order coaches.

[citation needed] In 1945, Kenworth was sold to Pacific Car and Foundry; both companies believed bus production would play a pivotal role in jumpstarting a postwar economy.

Kenworth also saw the opportunity in hiring former military truck and aircraft workers as part of launching its post-war product line.

Production of the T-126 averaged over 375 buses per year, making it Kenworth's most lucrative bus offering in the company's history up to that time.

Shortly afterwards, PC&F sold all rights, tooling, and equipment to school bus manufacturer Gillig Bros. of Hayward, California.

This is likely due to a number of factors including Kenworth's current status as a leading manufacturer of Class 8 heavy-duty semi trucks, and the fact that hardly any examples of Kenworth-built buses exist today (with exception of a few surviving model CT-73 "Pacific School Coach" buses and one remaining "Bruck").

[citation needed] In 2006, at the American Truck Historical Society's 11th Annual Truck Show at the Mason County Fairgrounds in Shelton, Washington, a historical society dedicated to preserving the Gillig Transit Coach and Kenworth-Pacific School Coach was officially dedicated.

[citation needed] The brand claims to maintain an image of high quality, it has won five of six JD Power Awards in 2005, and was a clear sweep in the 2007 J.D.