Queen Elizabeth is officially the oldest ruling head of state, 4 out of 5 UK residents were not born when she became Queen

Queen Elizabeth II has ruled for so long that most people in the United Kingdom have never known another monarch.

She became queen when her father, King George VI, died on February 6, 1952 (though her official coronation was on June 2, 1953).

During her reign, she has outlasted 14 British prime ministers and 13 US presidents.

After Robert Mugabe was ousted as president of Zimbabwe on Tuesday, the Queen became the world's oldest head of state, at 91 years old.