In 1965, Medicare was created to provide health insurance for the nation's seniors beginning in 1966. Forty years later, the program covers over 42 million people - primarily seniors but also others under age 65 with permanent disabilities. Medicare helps pay for a range of medical services, including hospital stays, physician visits, preventive benefits, and starting in 2006, prescription drugs. This timeline provides an overview of the legislative changes that have shaped the Medicare program over the past four decades.