The company�s founder Edgar Worthington unveiled his first truck in 1915. This was a six-cylinder model with a structural steel frame. He joined with Harry Kent in 1923 and Kenworth was formed. The headquarters was established in Seattle, Washington.

Marking their 70th anniversary the Renton plant was opened in 1993. This was the third plant in the United States. It has maintained its size of 360,000 square feet to date. Soon after construction the plant had reached the output of 17 trucks a day. Within a couple of years the T600 AeroCab was developed. This model was designed by the Kenworth Drivers board and greatly improved the existing T600B. Thus the marking the beginning of the consistently increasing production volume at the Renton facility.

The models assembled here currently include class 8 trucks. A class 8 truck is defined as one that weighs 80,000 lbs gross (before load).

This includes:
--T600 series
--T800 series
--T900 series

The trucks are assembled at this site; there is no manufacturing or machining. All vehicles are pre-sold with the various and numerous (6,500) customer specifications. Because of this, there is minimal automation in this facility.

With the installation of an Industrial Engineering team, the plant now produces 51 trucks a day without expansion of the facility. They have implemented such techniques as "Just In Time" enabling the correct chassis to meet with the correct cab assembly at the same time in the process. Each truck is different, so this proved to be difficult because it takes up to twice as long to assemble the cab then it does the chassis. This location is now one of six plants and assembling the most trucks per square foot.