The Medicare system, which exists in the United States today, is a social insurance program intended to provide health insurance coverage for people aged 65 and over, plus some other special groups such as disabled people. US Medicare is a single-payer health care system, and as such it is similar to Medicare in Canada and Australia, and to the NHS in the UK, except that American Medicare only covers a certain proportion of the population. This article covers the history of Medicare from its founding in the 1960s, to the funding challenges it faces today.