WASHINGTON - The Prince of Wales and his wife, Camilla, the Duchess of Cornwall, have had a jam-packed U.S. visit, which concludes Friday in Louisville, Ky., after three days in Washington.

But the royal visit isn't just about sightseeing at such landmarks as Mount Vernon and the Lincoln Memorial.

It's also about developing goodwill and promoting causes.

Prince Charles, a committed conservationist, spoke in Washington of his work preserving marine life, received a conservation award named for President Teddy Roosevelt, and made a surprise visit to a Smithsonian museum to discuss a coming exhibit on the ancient arts and crafts of Kabul, Afghanistan.

In Louisville, he will give a speech, the marquee event of the trip, in the city's Cathedral of the Assumption, on the connection of health and land and sustainability in agriculture. Charles and Camilla, in keeping with the theme, will visit a food literacy project for young people at a local farm.

British Ambassador Sir Peter Westmacott, using the acronym for nongovernmental organizations, described Charles at an event this week as "a one-man NGO."

At the White House Oval Office on Thursday, President Obama told Charles while the press was briefly allowed in the room, "I think it's fair to say that the American people are quite fond of the royal family."

"That's awfully nice to know," replied.

Then Obama added, "They like them much better than they like their own politicians."

Charles, 66, heir to the throne, has spent years promoting conservation through the multimillion-dollar Prince's Trust and other organizations.

"Prince Charles is a fantastic convener," said John Gantt, president of the International Conservation Caucus Foundation, which gave the prince the Teddy Roosevelt International Conservation Award on Thursday evening - a bronze and marble sculpture of a herd of elephants - for "his extraordinary conservation leadership."

By using the draw of his royal name and rank, Gantt said, the prince brings leaders in the private and public sector together on such issues as fighting elephant poachers in Africa, educating against deforestation, and cleaning oceans.

In a stop that was not posted on his itinerary, the prince visited the Freer Gallery of Art and Arthur M. Sackler Gallery, the Smithsonian's museums of Asian art.

He leads a nonprofit to rebuild the historic old city of Kabul and to promote its arts and crafts. The galleries are planning an exhibition next March featuring the Afghan arts and his foundation's architectural restoration work.