In his eight years at the helm of America's central bank, Jerome Hayden Powell has guided the U.S. economy through extreme tumult and fought off unprecedented presidential efforts to undermine the Federal Reserve's independence. But that's not what I'll tell my now-young children about Powell once they're old enough to care about central bankers. The big picture: It is Powell's approach to duty and public service that is his ultimate legacy as a leader and that will shape his place in history.