[Dr. Franklin]

That was the old Virginia accent. It changed after the Civil War. Maybe it was the Upcountry changing the Lowland accent, or maybe it came up from the Deep South as Virginians wanted to sound more “Southern.” Lowland and City people whose speech sounded more like British English before the war, may have tried to sound more “country” after the war because that was more “Southern.”

I noticed that too. Accents change over time. Recordings are good to remind people of that fact.

The accent did sound a little British. Listen to educated Brits in WWII documentaries. They have a different accent there now. It's sounds curious when I watch a British historical drama. I notice the "posh" accent is wrong for the time period.

[x]

That's the problem with historical dramas. If you make it completely accurate historically, today's audiences won't relate to it. If you want upper class characters to talk like actual Edwardian aristocrats, the audience would think they were all pompous, pretentious, and comical or villainous. It also happens the other way, though. It took a while for the upper class accent to form. Go back far enough and your aristocrats might have sounded more like peasants, and that won't do today either.

Old, upper class East Coast accents had a lot of British in them. They weren't always the same as regional accents. An upper class Bostonian, Philadelphian and Charlestonian might have sounded more like each other than like back country speakers in their regions. Maybe what we hear now as "British" was more the absence of strong American regional accents, than anything specifically British.