Buoyant one moment, the suddenly subdued dignitaries and automakers stepped into a trap Monday when St. Charles County Executive Steve Ehlmann asked for a moment of silence.
"Hear that tractor?" Ehlmann asked impishly. "That's the sound of progress in St. Charles."
Nixon hailed the announcement as part of the "rebirth of the American auto industry."
GM first announced the investment in November. The $380-million expansion will build a half-million square foot addition to its existing 3.7 million square foot plant.
Building GM's next generation Colorado will bring an additional 1,260 hourly and salaried jobs in 2013.
Some workers at the GM facility now producing the Colorado in Shreveport, La. are expected to accept the company's offer to move to Missouri.
But Mike Bullock, the chairman of UAW Local 2250 said he expects up to 80 percent of the jobs might ultimately be filled by St. Louis area residents.
The Wentzville plant, which shed 900 jobs during the recession, had 450 hires last year when it brought back a second production shift.
"It's great to be growing rather than shrinking," said plant manager John Dansby.