Production will end Thursday on the local plant's Isuzu line that dates back to 1994. Fifty-seven production workers will lose their jobs.

GM spokesman Chris Lee said another 40 to 50 employees in skilled trade will work to decommission the plant that after nearly 90 years is no longer in the automaker's immediate production plans.

GM said last June it would end local production of light-duty trucks—Suburbans, Tahoes and GMC Yukons—by the end of 2010 at the latest. It also said it would shut down the medium-duty Isuzu line sometime in 2009.

SUV production ended in Janesville on Dec. 23, a little more than five months after the plant lost a second shift of production. More than 2,000 hourly and salaried GM workers were laid off as a result of the production cuts. Supplier companies laid off another 1,200 people.

For the Isuzu line, "sometime in 2009" means Thursday.

Vehicle production at the Janesville plant can be traced to 1919 and the Samson Model M tractor. Chevrolet production started in Janesville in 1923.

GM and Isuzu strengthened a partnership in 1994 with the launch of the NPR gas-powered trucks in Janesville. Two years later, GM and Isuzu started a separate project that put Isuzu-designed cabs on GM's medium-duty chassis. That line eventually moved from Janesville to Flint, Mich.

What remains in Janesville—until Thursday—is the NPR "W" series. The cab-forward truck is Isuzu designed and engineered, has a GM power train and is commonly used as a delivery vehicle.

The Isuzu line and its employees have been producing about 25 trucks four days a week.

What will happen with the 4.8 million-square-foot plant that sits on 250 acres on Janesville's south side is uncertain.

GM spokesman Dan Flores said GM works hard to ensure that its surplus properties become productive for their communities.

Typically, the automaker takes one of three paths to dispose of property.

GM sometimes sells the property with some or all of its buildings demolished.

In rare cases, the automaker will transfer ownership to a nonprofit organization.

In most cases, GM will work with others to redevelop the property into shopping centers, industrial or recreational parks or for a variety of other uses.

All three options include a detailed review of the property and a decommissioning process, Flores said. Equipment that can be used in other GM facilities will be transferred, while other materials and equipment will be recycled.

The assessment also will include an environmental assessment that includes soil and groundwater testing. If a cleanup is necessary, GM will develop a remediation plan in conjunction with state and federal environmental agencies.

"We have to make a careful assessment of what we want to do with the plant," Flores said. "Before that's done, it's way too early to speculate on what will be done with the Janesville plant."