The boundary between the North and midland dialects in ohio represents an unusually clear opportunity to test how well dialect boundaries can persist. For part of this boundary, the original settlement by European Americans was strongly segregated: the area north of the line was heavily dominated by settlers from a hearth running from western New England through upstate New York, while the area south of it was dominated by settlers from a hearth comprising southern Pennsylvania, western maryland, and northern Virginia and West Virginia. recordings of Dictionary of American Regional English survey subjects, born 1880-1908, were compared with subjects, born 1970-94, from a new survey. A number of variables involving vowel quality or vowel mergers that are known or suspected to differentiate the North and midland were analyzed in these subjects' speech. Eight variables showed statistically significant differences according to dialect region. When these variables were combined quantitatively, the patterns that emerged are that the North and midland remain robustly differentiated but that a transition zone has developed along the boundary.