Medicare is a federal health insurance program established by the US Congress in 1965 as Title 18 of the Social Security Act. Coverage began in July of 1966. Medicare is designed to assist individuals aged 65 and older, some disabled individuals under the age of 65, as well as patients with end-stage renal (kidney) disease (ESRD). Medicare coverage is tied to eligibility for Social Security or Railroad Retirement benefits. However, persons receiving early retirement benefits from Social Security are not eligible for Medicare until they turn 65. Medicare enrollment is handled by the Social Security Administration. Unlike Medical Assistance, Medicare is not based on income or assets. About 35 million elders and about 4 million disabled persons are enrolled nationwide. In the Balanced Budget Act of 1997, Congress established an addition to the Medicare program, referred to as Medicare Part C or Medicare + Choice. The Medicare Prescription Drug, Improvement, and Modernization Act of 2003 changed the name of Medicare + Choice to Medicare Advantage and established another addition to the Medicare program, referred to as Medicare Part D.
Source: An Introduction to Medicare. SeniorLAW. Legal Action of Wisconsin, Inc. 29, Oct. 2003