Opened in 1919, it was the oldest operating GM plant when it was largely idled in December 2008, and ceased all remaining production on April 23, 2009.

[5] During World War II, the Janesville plants were taken over by General Motors' Oldsmobile Division, and produced artillery.

[5] In 1969, the Chevrolet and Fisher Body factories joined to form the General Motors Assembly Division.

[5] In the 1980s General Motors moved large car production from Janesville and started making subcompact J-cars, such as the Chevrolet Cavalier.

[5] Local efforts resulted in GM moving medium-duty truck and full-size sport-utility production from plants in Michigan to Janesville.

[8] In 2006, the Janesville GM Assembly plant achieved a milestone of producing more than 500,000 full-size sport utility vehicles with E85 FlexFuel capable engines.

In 2007, discussion of greenhouse gas fuel emissions regulations sparked a dialogue about the future of the Janesville GM plant.

[10] In 2008, fuel prices, the related slow sales of SUVs, and the economy resulted in GM cutting back full-time production at the Janesville plant to a single shift.

The factory was one of three — along with Orion Assembly and Spring Hill Manufacturing - that General Motors kept on standby during their bankruptcy.

[20] As of January 2016, GM had signed a new contract with the United Auto Workers that cleared the way for selling the Janesville plant.