Biggest center in the world for the manufacture of automobiles

Toyota had Become the world's largest auto manufacturer in 2007. Prior to that General Motors (GM) had held that position in the market for decades. There is currently a battle for first really, as GM continues to expand despite financial difficulty. 

GM's assembly plant complex in Oshawa was the reigning champion in North America from 1999 to 2006 and one of the largest automotive assembly facilities in the world. GM's Oshawa plant was overtaken in production numbers in 2007 by Toyota's Georgetown, Ky assembly plant. Georgetown assembled a staggering 514,000 cars and trucks last year, Oshawa produced 420,000. In previous years the Oshawa plant had produced over 500,000 vehicles per year as well. 

That would make, Toyota's Georgetown, Kentucky location the highest in overall production numbers, though not literally the "largest facility in the world." 

The Georgetown facility is an estimated 7.5 million square feet, while the GM Oshawa plant has over 10 million. They have since terminated some operations at the GM facility, which lead to Toyota's production number victory in 2007. 

The largest truck manufacturing facility is owned by Daimler Trucks division in Germany its 2007 revenue topped 28 billion Euro last year. They held the top spot in the commercial vehicles market with more than 20 percent of the worlds market share.