Speculation has heated up that Lloyd Blankfein could step down as Goldman Sachs CEO as soon as this summer. Blankfein is one of the only big bank chiefs who kept his job after the financial crisis, but many corporate governance experts believe a changing of the guard could go a long way toward helping the nation's biggest financial institutions repair their reputations. Sources tell Fortune that president and chief operating officer Gary Cohn is the lead candidate to replace him. Blankfein isn't the only leader to see Goldman Sachs through booms and busts. Here is a quick look at the executives who have shaped the investment bank for more than four decades.