Prince William Thanks 'Hardy Bostonians' for Braving the Rain on First Official Outing in Boston

Kate Middleton and Prince William are taking in the city of Boston.

The Prince and Princess of Wales touched down in the capital of Massachusetts on Wednesday for their three-day visit to the U.S. For their first official event of the trip, the royal couple appeared at Boston City Hall alongside Mayor Michelle Wu to start the countdown to the second annual Earthshot Prize Awards ceremony on Friday by lighting Boston City Hall and landmarks across the city green.

Prince William, Massachusetts Governor-elect Maura Healey, Boston Mayor Michelle Wu and Reverend Mariama White-Hammond each gave short remarks ahead of the lighting ceremony.

As he took the stage, William told the excited crowd gathered outside Boston City Hall, "Thank you to Mayor Wu and thank you to all the hardy Bostonians braving the rain!"

"There are two reasons why Boston was the obvious choice to be the home of the Earthshot Prize in its second year," he continued. "Sixty years ago, President John F. Kennedy's "Moonshot" speech laid down a challenge to American innovation and ingenuity. 'We choose to go to the moon,' he said, 'not because it is easy but because it is hard.'

Chris Jackson/Getty Prince William, Kate Middleton, Governor-elect Maura Healey and Mayor Michelle Wu

"It was that Moonshot speech that inspired me to launch the Earthshot Prize with the aim of doing the same for climate change as President Kennedy did for the space race. And where better to hold this year's Awards Ceremony than in President Kennedy's hometown, in partnership with his daughter and the Foundation that continues his legacy.

Prince William and Kate Middleton

"Boston was also the obvious choice because your universities, research centers and vibrant start-up scene make you a global leader in science, innovation and boundless ambition. Mayor Wu, you have also been a leader in putting climate policies at the heart of your Administration. Thank you.

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"Like President Kennedy, Catherine and I firmly believe that we all have it in ourselves to achieve great things, and that human beings have the ability to lead, innovate and problem-solve."

ANGELA WEISS/AFP via Getty Crowds gather outside Boston City Hall

There were cheers from the more than 1,000 people gathered to see the couple as they stepped onto the stage.

Molly Twomey, a local woman who was in the crowd, told PEOPLE: "I've always loved the royals. I remember waking up in the morning for Prince William and Princess Kate's wedding and watching it. I also studied abroad in London. I've always had a fascination with the royal family, so for them to come to my hometown, I couldn't miss it!"

"I think they're just so elegant," she says of the Prince and Princess of Wales. "I love that they have that family aspect. Kate's just so fashionable — I just think she's so stunning. As an American, it's just an exciting thing to see a royal family, it's something we don't have. To have them come, it's so exciting, especially because they'll become King and Queen eventually."

Chris Jackson/Getty Prince William

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Earlier in the visit, William and Kate met Mayor Wu's husband Connor Pewarski and their sons Blaise and Cass during a brief audience in the mayor's office.

The heir to the throne thanked Wu and the people of Boston for supporting the Earthshot Prize Awards.

"Thank you so much for your help," he said. "I think people are excited about the awards."

Chris Jackson/Getty Prince William and Kate Middleton

William and Kate stopped to look at framed photographs of Queen Elizabeth and Prince Philip with former Mayor of Boston Kevin White that were taken during a royal visit to mark the American bicentennial in 1976.

"1976, amazing isn't it?" said William.

Kate and Prince William's visit to Boston is significant for a number of reasons: not only is it the first time Prince William has brought his Earthshot Prize Awards overseas, but it marks their first international royal visit since becoming the Prince and Princess of Wales following Queen Elizabeth's death in September.

It is also their first visit to the U.S. since 2014 when they spent time in New York City. The couple also visited Los Angeles shortly after their 2011 wedding.

Prince William refers to the Earthshot Prize Awards as his attempt to provide some urgent optimism about tackling environmental issues and climate change. William and Kate, both 40, are "excited to be able to bring that to the United States and inspire people stateside and around the world through the incredible stories we are going to tell," a source tells PEOPLE.

Chris Jackson/Getty Kate Middleton and Prince William

The source adds, "The prize has become the Prince's Superbowl moment of the year, and he looks forward to continuing to use the platform each year to shine a light on some of the most impactful projects doing amazing things around the world to save our planet's future."

Prince William revealed they would be heading to the city of Boston back in July — fittingly, on the 53rd anniversary of the moon landing. Inspired by President John F. Kennedy's famed 10-year goal of landing on the moon (known as Moonshot), the Earthshot Prize aims to promote impactful approaches to the world's most pressing environmental challenges.

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To promote their environmental mission, the couple will travel in a hybrid Range Rover during their visit. They will also be keeping sustainability in mind when it comes to their style and the details around the Earthshot Prize Awards ceremony.

"We have asked everyone who is coming [to the Earthshot Prize Awards] to think about their clothing and think about how it can be reused, recycled or have a sustainable element to it," says Hannah Jones, CEO of the Earthshot Prize.

"Considerable amount of attention has gone into the show," Jones says, adding that the ceremony will feature three acres of plants, including New England-grown mixed evergreen and deciduous trees, on the green carpet and at the show.

Chris Jackson/Getty Prince William and Kate Middleton

All the flowers have been grown within 100 miles of the MGM Music Hall and will be donated to local community-based organizations after the show. The green carpet is the same one that was used at last year's show 2021 and will be recycled after the event. All energy use is being monitored and there is no single-use plastics.

Ahead of Friday's glamorous awards ceremony, Prince William and Kate will also visit organizations working to support causes close to their hearts. On Thursday, they'll tour Greentown Labs to learn more about the climate-related challenges that Boston faces, followed by a visit to Roca, a non-profit organization working to bring public systems together in a cohesive approach to change the trajectory of the lives of high-risk young people.

On Friday, Kate will visit Harvard University's Center on the Developing Child to learn about the scientific advances that can inform her work tied to improving the early years of a child's life. Meanwhile, Prince William will tour the John F. Kennedy Presidential Library and Museum with Ambassador Caroline Kennedy, his daughter.