While touring the First African Baptist Church, Stewart seemed confused that the tour guide spoke of the ventilation holes in the floor though which "people crawled under to escape slavery," but forgot to mention the Underground Railroad.
"There has to be an opening for the railroad," she said.
The rest of the wives had mixed reactions to Stewart's comments, while Phaedra Parks took the high road and explained that there really "wasn't a train" and that it was just "a euphemism, baby."
Kenya Moore said it was "almost hurtful to watch her be so dumb."
Meanwhile, NeNe Leakes, 45, simply said, "Ding. Dong."
Stewart's divorce from NFL star Kordell Stewart has been one of the main plots during Season 6 of the reality show, which began in early November. But according to sources, the 31-year-old ex-housewife could be cut from the show as soon as next season as producers believe her storyline is "a mix of boring and annoying" and "neither is good for TV."