This study compares vowel spaces in three regional varieties of American English spoken in central Ohio, south-central Wisconsin, and western North Carolina to determine whether the significant variation in the vowel systems of these dialects also affects the dialect-specific vowel space area. The gender-related differences are assessed by comparing the unnormalized (in Hz) and normalized formant frequency values. Significant effects of speaker dialect were found for the vowel space area defined by four corner vowels. However, there were no differences between dialects in the area of an extended 5-vowel space. The results indicate that, despite large cross-dialectal differences in the positions of the vowels in the acoustic space, the extended vowel space area encompassing a complete vowel system is unaffected by dialectal variation. The differences in the size of the vowel space due to speaker gender were eliminated by normalizing formant frequency values.