The Prince of Wales and the Duchess of Cornwall were met with icy temperatures as they arrived in Philadelphia.
Charles and Camilla met the crowds on their tour of Philadelphia
Charles followed in the footsteps of his great-great-grandfather Edward VII who toured the American city in 1860 when he was Prince of Wales.
More than 400 people greeted the couple outside the city's Independence Hall.
In a speech at the National Constitution Centre the prince said he was "enormously proud" to be following in his ancestor's footsteps.
Camilla arrived in Philadelphia in a Robinson Valentine grey cashmere coat with fake chinchilla trim but without a hat despite the freezing weather.
In his speech, Charles said: "My predecessor's programme included the hugely accomplished Academy of Music where I will be this evening for the 150th anniversary concert.
"He also visited Girard College where he planted a tree that still stands which I can only assume is a testimony to the remarkable powers of green fingers."
The prince also touched on the relationship between the UK and the US.
"I am so pleased that Britain and America are working closely together to share our most innovative and effective ideas," he said.
Charles was welcomed at the civic reception by the governor of Pennsylvania, Ed Rendell.
Animal rights group People for the Ethical Treatment of Animals (Peta) staged a protest over the use of real fur used in the Queen's guards head-dresses.
Charles and Camilla also saw the city's famous Liberty Bell, with its distinctive crack down the side.
The couple will attend a white-tie concert at Philadelphia's Academy of Music where the bill includes rock star Rod Stewart.
The prince and the duchess travelled to the US on a scheduled British Airways flight from Heathrow, although its departure was delayed by nearly an hour.
Charles has been criticised by 'green' campaigners for flying to the US to pick up an environmental award in New York.