This study examines cross-generational changes in the vowel systems in central Ohio, southeastern Wisconsin and western North Carolina. Speech samples from 239 speakers, males and females, were divided into three age groups: grandparents (66-91 years old), parents (35-51) and children (8-12). Acoustic analysis of vowel dynamics (i.e., formant movement) was undertaken to explore variation in the amount of spectral change for each vowel. A robust set of cross-generational changes in /ɪ, ε, æ, ɑ/ was found within each dialect-specific vowel system, involving both their positions and dynamics. With each successive generation, /ɪ, ε, æ/ become increasingly monophthongized and /ɑ/ is diphthongized in children. These changes correspond to a general anticlockwise parallel rotation of vowels (with some exceptions in /ɪ/ and /ε/). Given the widespread occurrence of these parallel chain-like changes, we term this development the "North American Shift" which conforms to the general principles of chain shifting formulated by Labov (1994) and others.