When the Social Security Act of 1965 was signed into law by President Lyndon B. Johnson, Medicare was formed, creating a government-run public insurance option for United States citizens aged 65 or over.

Today, Original Medicare (Parts A and B) is administered by the Department of Health and Human Services through the Centers for Medicare and Medicaid Services (CMS). While Medicare offers a solid foundation of health care coverage, there are holes which some beneficiaries choose to fill by purchasing private plans.