Speech sounds are the result of coordinated movements of individual articulators. Understanding each articulator's role in speech is fundamental not only for understanding how speech is produced, but also for optimizing speech assessments and treatments. In this paper, we studied the individual contributions of six articulators, tongue tip, tongue blade, tongue body front, tongue body back, upper lip, and lower lip to phoneme classification. A total of 3,838 vowel and consonant production samples were collected from eleven native English speakers. The results of speech movement classification using a support vector machine indicated that the tongue encoded significantly more information than lips, and that the tongue tip may be the most important single articulator among all of the six for phoneme production. Furthermore, our results suggested that the tracking of four articulators (i.e., tongue tip, tongue body back, upper lip, and lower lip) may be sufficient for distinguishing major English phonemes based on articulatory movements.