* Possible Origins: The show never explicitly states where Mary is from, but she is portrayed as having a relatively neutral American accent. This suggests she might be from a region known for its "general American" speech pattern, like the Midwest or parts of the East Coast.
* Show's Emphasis: *Mad Men* focuses heavily on the characters' social class and regional identity. While Mary's accent is not a central part of her characterization, the show is known for subtle details and the way characters speak can be a subtle indicator of their background.
* Actor's Accent: The actress who plays Mary Draper, Amber Tamblyn, is from California and has a standard American accent. However, actors often adopt accents for roles, so it's possible she might have been instructed to speak with a particular regional accent for the show.
In conclusion: While we can't be certain about Mary Draper's accent, it's likely that she spoke with a relatively neutral American accent, potentially reflecting a Midwestern or East Coast background. The show's emphasis on social class and regional identity might have played a role in the portrayal of her accent.