The child will be third in line to the throne behind Prince Charles and Prince William. Prince Harry will now be bumped down to fourth. The laws of succession were recently changed, meaning a daughter would not be bumped by the arrival of a little brother.
William and Kate have been tight-lipped about potential names -- so far. It is believed they have drawn up a shortlist but are waiting for the baby's arrival before making a final decision.
Charles and Diana waited a week before announcing their son would be called William, Prince Andrew and Fergie took two weeks over Princess Beatrice and the Queen took a whole MONTH before giving Prince Charles his name.
The world learned of the baby's birth in the same way the births of generations of royals have been announced, with a note on the front gate of Buckingham Palace. It was the same way we learned about William's birth. The easel hasn't been used since it announced William's arrival in 1982.
Kate gave birth in the Lindo wing of St Mary's Hospital in Paddington.
Prince William is following modern convention by taking paternity leave. He is expected to take the two weeks paid leave offered by the Ministry of Defence. He will then return to his job as an RAF search and rescue pilot. Statutory paternity leave has only been in force in the UK since 2003.
The birth was in a hospital. While it might seem obvious that the Duke and Duchess of Cambridge's baby would be born in a hospital, Prince William was actually the first would-be king to arrive in such a way. Both he and his brother Prince Harry were born in the private Lindo Wing of St Mary's Hospital in Paddington, west London, where the duchess will give birth. The Queen gave birth to Prince Charles and Prince Andrew at Buckingham Palace.
The birth due date fell in the middle of the Coronation Festival, a four-day celebration to mark 60 years since the Queen was crowned, 16 months after being proclaimed Monarch on her father's death.
They were wrong! According to two of Great Britain's most popular betting sites - Ladbrokes and Paddy Power - the royal couple were going to have a little girl and will name her Alexandra.
According to a royal historian, William will be the first-ever father in the delivery room for a royal birth.
Under protocol, the Foreign Office still informed all British missions around the world about the royal birth by diplomatic telegram. British diplomat Dominick Chilcott told The Washington Post: "In the days before the 24/7 media, far-flung diplomatic missions might have got their news first by diplomatic telegram, depending how well they could tune their radios to the BBC World Service short wave signal. And especially in Commonwealth countries and other places with close connections to the Royal Family, it would have been an important duty to inform the local government about the birth of a royal baby in line to the throne. Diplomatic telegrams these days are very different from how they were even when I joined the Diplomatic Service 30 years ago. Then, they were the only form of rapid written communication and involved staff at either end sending and receiving the message. Now, they're really just a particular kind of email."
The christening robe will be a replica of one that has been used since 1841.
The baby will fall under the zodiac sign of Cancer, just like Prince William, who was born on June 21, and his mother, the late Princess Diana, who was born on July 1.
The due date was believed to be July 13, although the Palace never officially announced it.