Nearly 15 years ago, a family trust in California purchased 1,100 acres about 25 miles southwest of Raleigh hoping to attract a company that wants to build something big on the edge of one of the fastest-growing metropolitan areas in the country. Today, the site has doubled in size to 2,285 acres and is nearly ready to be developed. The property owners and local officials hope the so-called megasite will attract an automotive, aviation or other large manufacturer to give the region, particularly Chatham, Harnett and Lee counties, an economic boost.