On 21st April 1926, Princess Elizabeth Alexandra Mary was born at her paternal grandfather's home on 17 Bruton Street in London's Mayfair neighborhood. When her uncle, King Edward VIII abdicated the throne in 1936, Princess Elizabeth became heir to the British throne.
87 years after her birth, Queen Elizabeth II follows Queen Victoria as the longest-reigning sovereign in British history. Should she remain on the throne through September 9th, 2015, Queen Elizabeth II will surpass her great-great grandmother reign.
Her Majesty chose to celebrate her birthday "in private" at Windsor Castle today.