Final answer:
The Federal Reserve Act, signed into law in 1913, created the Federal Reserve System, which is the central banking system of the United States. This act has managed the U.S. economy for over a century by regulating the money supply and interest rates.
Step-by-step explanation:
The act that was signed into law, creating a system that successfully managed the United States economy for over 100 years, is b) The Federal Reserve Act. Passed in 1913 and signed by President Woodrow Wilson, this act established the Federal Reserve System, America's central banking system. The Federal Reserve, often referred to as the Fed, provides a financial safety net, controls the money supply, and regulates interest rates through mechanisms like the federal funds rate. This framework aimed to provide stability in times of economic distress by making monetary policy more responsive to the changing needs of the economy.
The creation of the Federal Reserve was in response to several banking crises that had demonstrated the need for a more robust banking system. Through the establishment of 12 regional Federal Reserve Banks and the central Federal Reserve Board, the system can adjust the discount rate to influence borrowing and manage economic fluctuations. As a result, by 1923, the Federal Reserve Act had brought approximately 70% of the nation's banking resources under the umbrella of the Federal Reserve System, thus laying the foundation for modern American banking and economic policy.