The royal baby has arrived

Maria Puente and Kim Hjelmgaard | USA TODAY

LONDON -- Get ready for a 62-gun salute, watch the water in the fountains turn blue, let the fireworks and street parties commence: The royal baby has arrived, and it's a boy.

Prince William and Duchess Kate's first baby, a future monarch, was born today at 4:24 pm local time in London's private wing of St. Mary's Hospital, the palace announced. The announcement said the baby weighed 8 pounds, 6 ounces, and William was present for the birth.

In a statement, Prince William said: "We could not be happier."

Mother and baby were both doing well, the announcement added. The name was not immediately announced. There's a chance it could be announced as early as Tuesday, but it's also possible it may not be known for some days.

The news was supposed to be first announced in the traditional manner, on fancy paper with a Buckingham Palace letterhead on a gilded easel at the palace front gates. Instead, it went out by electronic press release first, to the royal Twitter feed and websites, and then proclaimed from every TV and computer screen in the country.

After that, the framed announcement went up on the easel at the gates, watched and cheered by a growing crowd despite what was being called the hottest day in London in years.

But the baby's great-grandmother, Queen Elizabeth II, was the first to get the news from her grandson, by encrypted phone to the palace, and just in time, too. She's scheduled to leave on her annual vacation at her Balmoral estate in Scotland at the end of this week.

The palace announcement said the royal family, including the queen's husband, Prince Philip, the baby's grandfather, Prince Charles the Prince of Wales, his wife, Camilla Duchess of Cornwall, and William's brother, Prince Harry, and other family members have been notified and are "delighted."

Prince Charles issued a statement saying he and Camilla are "overjoyed" and "thrilled" for the couple.

"Grandparenthood is a unique moment in anyone's life, as countless kind people have told me in recent months, so I am enormously proud and happy to be a grandfather for the first time and we are eagerly looking forward to seeing the baby in the near future," the first-in-line to the throne said.

Prime Minister David Cameron came out of Number 10 to hail the "wonderful news" and the "important moment in the life of the nation."

President Obama and first lady Michelle Obama congratulated the couple on "the joyous occasion" of the birth.

"We wish them all the happiness and blessings parenthood brings," the Obamas said in a written statement. "The child enters the world at a time of promise and opportunity for our two nations. Given the special relationship between us, the American people are pleased to join with the people of the United Kingdom as they celebrate the birth of the young prince."

In a separate message posted on Twitter, Mrs. Obama said: "Being a parent is the best job of all."

Speaking of Twitter, the company announced late Monday that more than 2 million tweets about the royal baby were sent out starting when Duchess Kate checked into the hospital early in the morning, reaching a royal-baby buzz peak of about 25,300 tweets per minute.

There was no word yet on whether Kate's mother and younger sister, Carole and Pippa Middleton, 29, were at the hospital for the birth.

The duchess was expected to spend at least one night overnight at the hospital, but it's possible she and William and the baby will emerge from the hospital as soon as today for the customary pose before the media, after three weeks of waiting, outside the hospital.

The birth of the royal baby was a model of the careful blend of traditional and modern exemplified by this royal couple in the dozen years they've been a couple. Plans call for a multi-gun salute near Buckingham Palace, probably on Tuesday, blue water running in the fountains, blue lights at the top of iconic buildings, fireworks and street celebrations throughout the land.

It's a boy! Kate Middleton gives birth to a baby boy. USA TODAY's Maria Puente and Alison Maxwell talk about the royal baby.

The baby arrives just short of 27 months since William and Kate were married in a spectacular ceremony at Westminster Abbey on April 29, 2011. The nine months of her pregnancy have been chronicled by the British and world media with excruciating detail and growing excitement about the first royal heir to be born in 31 years, since William himself was born to Prince Charles and Princess Diana.

(In fact, the last time the easel-and-note was used to announce a royal birth was for William.)

The baby moves immediately to third in line to the throne, behind father William and grandfather Charles. The queen is 87 and celebrating her 61st year on the throne.

The past few weeks saw rising royal-baby fever in Britain, with hopes high that the birth would provide an estimated $360 million boost in the flat British economy. Meanwhile, royal-baby doodads, such as Will and Kate masks, poured into shops for use at the street parties soon to break out all over the country.

The baby arrived a little late , based on a mid-July due date. Unlike the majority of births in Britain, no one, not even the parents, knew the sex of the baby until the birth.

The baby was the second royal heir to be born in a London hospital, the same one where William was born in 1982 (as well as other recent royal babies not close in line to the throne). The Lindo Wing of St. Mary's is a favorite birthing destination of London's rich and famous, with estimates of the cost of a natural birth in a private suite as high as $15,000.

William was in the delivery room, as was his father when he was born. He is taking two weeks off for paternity leave.

Many details about the birth were unclear, and some of the speculation was a bit unseemly. Kate had planned a natural birth, being "not too posh to push," as the Daily Mail put it. Did she employ a "hypno-birth" or some other birthing strategy to dull pain? Will she breast-feed the baby?

It seems likely the couple will take the baby and stay for a few weeks at Kate's parents' estate in the country, where there is a nursery. The couple live in a small apartment at Kensington Palace when they're in London and are not expected to move into more palatial digs until the fall.

If they stay at the Middletons' mansion in Bucklebury, Berkshire, that would mark the first time a royal heir spent the first few weeks of life outside a royal palace or estate. These details matter to the British.

Britain learned that the duchess had gone into labor after she checked in and settled at the hospital. In the age of Twitter, it was considered impossible to keep the news under wraps for long, so the palace announced it. (The palace was forced to announce Kate was pregnant ahead of schedule when she experienced acute morning sickness early in her pregnancy and had to be hospitalized.)

Palace press officials had arranged for a theatrical ritual if the baby was born during daylight hours: After the birth, the formal notice, signed by her doctors, would be brought out the front door of the hospital, handed to a driver and then driven with a police escort through London to the front of Buckingham Palace, where it would be placed on the easel. The birth of a royal heir is rare enough to warrant the trouble, palace officials said weeks ago.

But if the baby were born in the middle of the night? No midnight runs to the palace, no police escort. The news would go out in an electronic news release and the notice on the easel set up in the morning.