In this dissertation, I demonstrate that animacy of subject referents strongly conditions verbal morphosyntactic variation in English varieties. Using three quantitative case studies, I investigate copula and subject verb agreement in two English varieties, Mainstream American English (MAE) and African American Vernacular English (AAVE). For each of the case studies -- (1) MAE auxiliary contraction, (2) AAVE copula contraction and dele- tion, and (3) AAVE verbal -s deletion -- human subjects like the boy significantly prefer the contracted or null form, while non-human subjects like the book prefer the full or overt form. The first two case studies, MAE contraction and the parallel feature in AAVE, copula contraction and deletion, demonstrate that inanimate subjects predict the full form, while contracted and (AAVE) deleted forms are more likely with animate subjects. This finding supports Labov's 1969 analysis that AAVE contraction is similar to MAE contraction, and that AAVE contraction and deletion share conditioning constraints. The third case study, AAVE verbal -s, is widely considered not to be grammatically conditioned. However, I find that AAVE verbal -s is also conditioned by animacy, indicating that verbal -s is part of the underlying grammar. Taken together, I use these case studies to argue that animacy is a domain-general processing cue that grammars can structurally reify. These animacy effects in English shed new light on old variables. From a sociolinguistic perspective, we see that initially unintuitive and unexplored factors like animacy in English are robust predictors of variation. Furthermore, these results allow us to make progress on controversial aspects of grammatical analysis in AAVE, as well as refine our understanding of MAE morphosyntactic variation. These results may also be brought to bear in future discussions of the relationship between MAE and AAVE grammars. Finally, this dissertation contributes to the ongoing question in linguistic and psychological literature about the place of animacy in language, and how processing and grammar interact in linguistic conditioning. With animacy so significantly conditioning variation and having such profound theoretical implications, it is clear that future studies should give careful consideration to the role of animacy in language variation.