When Queen Elizabeth II was born, she was third in line to the throne — and considered highly unlikely to wear the crown.
Elizabeth was born Elizabeth Alexandra Mary Windsor on April 21, 1926, to then-Prince Albert, Duke of York, and his wife, Lady Elizabeth Bowes-Lyon.
Albert, who later became King George VI, was the second-oldest son of King George V, meaning the heir-apparent was his older brother, the then-Prince Edward.
Edward did rise to the throne following the death of his father in 1936, using the title King Edward VIII. But Edward shocked the world when he abdicated the throne less than a year later so he could marry American socialite Wallis Simpson, who, controversially, was twice-divorced.
Edward's abdication turned his younger brother into King George VI — and suddenly made Elizabeth into heir presumptive at age 10.As King George VI weathered the storm of World War II in Buckingham Palace, Elizabeth and her sister, Margaret, spent several years at Windsor Castle.
Elizabeth convinced her parents to let her join the women's branch of the British Army in 1945, making her the first woman of the royal family to be an active duty member of the British Armed Forces.
Elizabeth learned how to drive and service heavy vehicles during her time in the army, and later recalled the night the war ended as “one of the most memorable nights of my life.”
On her 21st birthday, Elizabeth proclaimed on the radio to Britain and the Commonwealth nations that “my whole life, whether it be short or long, will be devoted to your service.”
Later that year, she married Royal Navy officer Philip Mountbatten, a prince of Greece and Denmark, in a ceremony at Westminster Abbey. The couple had two children, Charles and Anne, prior to Elizabeth becoming queen.
King George VI died in 1952 at age 56 after years of poor health, and Elizabeth was told she was queen while on a trip in Kenya.
“In a way, I didn’t have an apprenticeship,” Elizabeth told a BBC documentary in 1992. “My father died much too young, and so it was all a very sudden kind of taking on and making the best job you can.”
Elizabeth's coronation ceremony took place in 1953 at Westminster Abbey, more than a year after her father's death. She also had two more children, Andrew and Edward, in 1960 and 1964.
Over Elizabeth's 70-year reign, she served as a symbol of stability through the changes of the 20th and 21st century. She met with 13 U.S. presidents and 15 British prime ministers, and was the longest-serving British monarch in history.
The queen celebrated her Platinum Jubilee in June, commemorating 70 years on the throne, though she canceled appearances at some events due to her health.
Elizabeth died on Thursday afternoon at age 96 at Balmoral Castle in Scotland, and her oldest son, Charles, immediately became king. A spokesperson for Clarence House confirmed to NBC News Charles has chosen the title of King Charles III.