The significance of the Social Security Act in U.S. history lies in its establishment of a social safety net for Americans. Enacted in 1935 during the Great Depression, the Act created programs for old-age benefits, unemployment insurance, and support for the disabled and families. It marked a shift toward a federal responsibility in addressing economic security, significantly enhancing the welfare state. Over the decades, it has evolved and expanded, providing critical financial support to millions of Americans and shaping the nation's social policies and economic landscape.