The Social Security Act of 1965 was signed into law on July 30, 1965, by President Lyndon B. Johnson as amendments to existing Social Security legislation. This legislation established the Medicare program.

Medicare is a social insurance program administered by the United States government, providing health insurance coverage to people who are aged 65 and over; to those who are under 65 and are permanently physically disabled or who have a congenital physical disability; or to those who meet other special criteria. The "Original Medicare" plan, i.e. Medicare without Medicare Advantage added on, coverage extends to 80% of any given medical cost; the remaining 20% of cost must be paid either a Medicare Advantage plan, which is a "supplemental insurance" from a private health insurance company, or with out-of-pocket via the patient's own personal funds.