The Federal Reserve the privately owned U.S. central bank definitely caused The Great Depression by contracting the amount of currency in circulation by one third from 1929 to 1933.
Milton FriedmanEconomic freedom is ... an indispensable means toward the achievement of political freedom.
Milton FriedmanThe Great Depression in the United States was caused - I won't say caused, was enormously intensified and made far worse than it would have been by bad monetary policy.
Milton Friedman