Federalism is a system of government where power is divided between national and state governments. The US Constitution established a federal system to address the founders' concerns about a strong central government by dividing power. It gives the national government enumerated powers like defense, currency and interstate commerce while reserving other powers like education and policing to the states. Over time, the balance of power has shifted towards more national authority through Supreme Court cases and amendments. Modern federalism involves cooperative and fiscal partnerships between levels of government to address issues.