This paper examines a hitherto undiscussed dialectological feature of Upstate New York: the pronunciation of words like elementary (documentary, complimentary, etc.) as eleméntàry, with secondary stress on the penultimate syllable. We report the results of three studies examining the geographic distribution of this feature. In the first study, data from 119 sociolinguistic interviews in communities in eastern New York establish the widespread usage of the feature in this region. In the second study, data from 59 sociolinguistic interviews in far western New York and northwestern Pennsylvania show that the geographic extent of the feature hews very close to the New York–Pennsylvania state line in that region. The third study is a rapid and anonymous telephone survey of the lexical item elementary including 188 towns across the entire state of New York and nearby parts of adjacent states. This study finds that the stressed-penultimate pattern is nearly confined to Upstate New York, bleeding only into the Northern Tier of counties in Pennsylvania and a few towns in southwestern Vermont. In addition to providing empirical evidence for the geographic extent of this dialectolgical feature, this study analyzes the relationship between the distribution of the -méntàry pronunciation and other isoglosses that serve as boundaries between major dialect regions in the area. The analysis shows that the geographic extent of the -méntàry pronunciation does not always pattern closely with dialect regions defined by phonological criteria; rather, it coincides more closely with the cultural boundary delimiting the region of Upstate New York. We argue that this type of linguistic boundary is caused primarily by communication patterns (as opposed to constraints internal to the linguistic system), and that it is more likely to be observed in variants involving analogical change, such as the -méntàry pronunciation.