The official announcement of Kate Middleton and Prince William's royal baby girl was posted on an easel outside Buckingham Palace on Saturday, May 2 Credit: Mark Cuthbert/UK Press via Getty Images

It's official! Kate Middleton and Prince William welcomed their first daughter, Princess Charlotte Elizabeth Diana, into the world in Paddington, London at St. Mary's Hospital on Saturday, May 2. And just four hours after her arrival, the official announcement for the royal baby was posted on an easel outside Buckingham Palace.

The gold easel was placed in the forecourt at 12:30 p.m., with the notice printed, signed, and framed by the medical staff at St. Mary's Hospital. The framed bulletin was brought out of the Privy Purse Door and will be on display for 24 hours. It will then be sent to the Privy Council Office so that it can be recorded in the Privy Council records.

The declaration is a tradition for the royal family. It was last used for the birth of Prince George in July 2013. (At the time, the easel was even driven over by police escort!) Like before, an insider tells Us Weekly that the Duke and Duchess of Cambridge will soon be visited by friends and family at St. Mary's Hospital. This time, however, their bouncing baby boy Prince George may be in attendance!

St. Mary's Hospital has been the chosen location for royal births since the 1970s. Before then, royal families traditionally welcomed their children at home.

Middleton and Prince William's baby girl is now the 11th known royal to be born at the facility. Other notable births include her grandmother Queen Elizabeth II, Prince Harry, and Peter and Zara Phillips. Her proud father Prince William was the first future king to be born there.

Us Weekly is on the scene outside St. Mary’s Hospital in London -- check out the exclusive royal baby livestream and check back often for ongoing updates on all things royal baby!