Before and during the American Revolution, the English, both in England and in the colonies, mostly spoke with a rhotic accent. The rhotic accent means that all hard r’s were pronounced, like “hard.” Once we had the first sound recordings after the American Revolution, some three hundred years after the colonists first settled in the New World, the accents of the British and Americans were discernibly different. The Americans had kept the rhotic accent.
But the British spoke with non-rhotic accents — “hard” was pronounced more like “hahd.” Sometime 1800s, not long after the Industrial Revolution, the non-rhotic accent appeared in southern England. It quickly spread, especially among the middle- and upper-class. Non-rhotic accents became signifier of class, so important in England — especially when traditional social statuses were being upended by the economic revolution. Because the Received Pronunciation (RP) accent was regionally “neutral” and easy to understand, it spread across England and the empire through the armed forces, the civil service and, later, the BBC. Along the seacoast of America, it caught on as well among the upper classes. And since the East Coast was the social and economic powerhouse of America through much of the 19th century, non-rhotic meant high-class in America. As industry shifted, though, areas with rhotic came back into power. General American (GenAm) which is used by broadcasters and radio hosts, is non-rhotic.
Now, of course, with the quickly shifting languages, most areas of both America and Great Britain do not use the standard accents. In the US, only a small part of the midwest uses GenAm. And in Great Britain, a smaller country with many more accents packed into it, only the upper class naturally uses RP.
(Source: mentalfloss.com)
