These big rigs still rule the road.

Kenworth has been building commercial trucks since 1923, and even then the company evolved from the earlier Gersix Motor Company that was in the same business. The company's name was a portmanteau of the two primary shareholders at the time Harry Kent and Edgar Worthington. To show how far things have come, the folks from Fleet Logging have created renderings showing the evolution of the important W900 and T600 series of models.

1961 Kenworth W900

If you have spent even the briefest amount of time on an American Interstate, then it is practically a certainty that you've seen a Kenworth W900 semi. The model debuted in 1961 and proved to be a success. In '61, Kenworth produced a total of 2,037 trucks across all of the company's offerings, which was a record for the time.

Compared to its predecessor, there was a raised roof for the cab, and the company moved the two panes of the windshield closer together, rather than separating them with a piece of metal previously.

1967 Kenworth W900A

The W900 received a big update in 1967 to become the W900A. The hood was now wider, which allowed for fitting even larger engines and bigger radiators. In 1972, a smaller change introduced bigger windows, and 1976 brought a new design available for the sleeper cabin that gave it a raised room for even more room.

The W900A also became a movie star by being the semi hauling 400 cases of Coors beer from Texarkana to Atlanta in Smokey and the Bandit.

1982 Kenworth W900B

The W900B replaced the A variant in 1982. Once again, revisions to the design of the hood allowed for fitting bigger engines. The exterior also adopted rectangular headlights, rather than the earlier over shape from dual, circular lamps.

Timothy Dalton does a stunt by driving a W900 on half of its wheels to avoid a rocket in License to Kill. Kenworth capitalized on the appearance by introducing a 007 Edition that came fully loaded with amenities and a longer wheelbase. The model proved successful enough that the company made the longer model a regular part of the lineup as the W900L.

2018 Kenworth W990

Introduced in 2018, the W990 is the latest evolution of the W900. Kenworth takes the classic look and loads it with modern tech. It offers amenities like predictive cruise control, electronic stability control, collision mitigation, and lane departure warning. The largest version offers a 76-inch sleeper cab and 19-inch side extenders. Inside, customers can specify a refrigerator upgraded stereo, a mount for a 28-inch TV, and a wardrobe with room for hanging clothes. The hauling power comes from a 12.9-liter inline-six diesel with up to 510 horsepower (380 kilowatts) and 1,850 pound-feet  (2,508 Newton-meters) of torque and a 12-speed automated transmission from PACCAR.

Kenworth W900 Front Timeline

1990 Kenworth T600A

Following the oil crisis in the 1970s, there became an interest in building more fuel-efficient semis. First introduced in 1985, the Kenworth T600 was the first heavy-hauling truck with a clean-sheet design with a focus on low-drag aerodynamics. Tweaks like sloping the hood and using smoother lines allowed for a 22 percent improvement in fuel efficiency than with a conventional straight hood.

The T600A (above) brought further improvements to the big rig. There was now two grilles at the front with a metal strip separating them vertically, rather than the previous single-piece design. Redesigned side mirrors integrated them into a single unit mounted to the cab. A curved windshield replaced the earlier flat design.

1995 Kenworth T600B

Kenworth continued the improvements with the T600B. The tweaks included a newly integrated cab and sleeper section. Later, the company changed the hood to have a three-piece design and offered different doors with a notched section for the windows to increase outward visibility.

2008 Kenworth T660

The T660 replaced the T600 in 2008. There was a new profile for the hood and fenders for improved aerodynamics. The headlights fully integrated into the front end.

2013 Kenworth T680

The T680 replaced the T660 in 2012, and Kenworth touted it as the "most aerodynamic truck in the company’s history." The version available now has features like predictive cruise control, lane departure warning, side object detection, predictive neutral coast, driver shift aid, and tire pressure monitoring. There are lots of engine options, including the same 510-hp 12.9-liter powerplant from the W990

Kenworth T600 Timeline Front End