Microsoft's Gates May Be Wealthiest American: Microsoft Corp. founder William H. Gates III appears to have become America's wealthiest individual, with his stock in the world's largest software maker worth nearly $6.5 billion. Microsoft shares jumped $2.75 Thursday to close at $114 in the first day of trading in 1992. The stock has risen more than 1,200% since Microsoft went public in the mid-1980s. Gates owns 56.7 million shares. The surge means that Gates' wealth surpasses the $5.9 billion attributed to John Warner Kluge in Forbes magazine's annual ranking of the wealthiest people in the United States, published in October. Kluge owns Metromedia, a communications company.