This article examines variation in American Sign Language (ASL) signs produced with a 1 handshape, which include signs of nearly all grammatical classes. Multivariate analysis of more than 5,000 tokens, extracted from informal conversations among more than 200 signers in seven different regions of the United States, indicates that variation in the form of these signs is conditioned by multiple linguistic and social factors. Significant factor groups include grammatical function and features of the preceding and following segments, as well as a range of social constraints including age, regional origin, and language background. Two findings are especially notable. First, although the results for preceding and following segment effects show evidence of progressive and regressive assimilation, grammatical function is the first-order linguistic constraint on the use of two of the three main variants. Second, signers in all regions of the United States show similar patterns of variation, thus providing evidence that ASL signers constitute a single “speech” community.