The article discusses the importance of sociohistorical context which is the foundation of variation studies in sociolinguistics. The studies on variation in spoken and signed languages are reviewed with the discussion of geographical and social aspects which are treated as external factors in the formation and maintenance of dialects and those factors often have historical roots. The Black ASL project is reviewed as a case with racial segregation and educational policies as part of the sociohistorical factors in the emergence of Black ASL.