We tested for the influence of gender, stream, and watershed on morphological variation in northern crayfish (Orconectes virilis) in Illinois. Crayfish collections spanning from 1950-present were analyzed from the Illinois Natural History Survey. We used geometric morphometrics to characterize shape and tested for differences among and within sites. Morphological variation is linked with adaptation and subsequent success of aquatic taxa. Disentangling the potential influences on crayfish morphology has implications for improved understanding of ecosystem structure and conservation.