Based on in-depth interviews of successful entrepreneurs, and on the biographers of his historical subjects, Gartner defines the hypomanic temperament and its manifestations. Then he demonstrates its power in action, offering some portraits that span America's history - Columbus who discovered America, John Winthrop who defined it, Alexander Hamilton who pointed to its future, Andrew Carnegie who built its fortune, Louis B. Mayer who glorified its ideals in movies, and Craig Venter, who is inventing its genetic future. Though these men are extraordinary figures, Gartner says many Americans carry the genes that have made them the most successful citizens in the world.