Boxing legend Muhammad Ali welcomed the Prince of Wales and Duchess of Cornwall to his home city of Louisville, describing Charles as "the greatest".
The sport star's words came in a letter rather than in person as he was not well enough to join leading figures from the city at a cultural greeting for the royal couple, who were in the city on the final day of their US tour.
Prince Charles has been awarded the Teddy Roosevelt International Conservation Award for his "extraordinary" conservation leadership.
The Prince of Wales accepted the award as he attended the International Conservation Caucus Foundation dinner.
Barack Obama told Prince Charles that American people rate UK royalty above their own politicians on the royal couple's Washington tour.
Watch Prince Charles try - and fail - to get a strike on the bowling alley during a trip to a veterans' retirement home in Washington.
Charles and Camilla spent a busy first full day of their US trip visiting memorials to President Abraham Lincoln and Martin Luther King Jnr.