This Element uses data from the Springville Project to explore how the functions of the inherited forms invariant be (from English sources) and zero (from creolization) have transformed during the twentieth century. Originally just alternative present tense copula/auxiliary forms, both features developed into aspectual markers - invariant be to mark durativity/habituality and zero to mark nonstativity. The motivation for these innovations were both socio-cultural and linguistic. The Great Migration and its consequences provided a demographic and socio-cultural context within which linguistic innovations could develop and spread. The mismatch between form and function within the present tense copula/auxiliary system and the grammatical ambiguities that affected both invariant be and zero provided linguistic triggers for this reanalysis. When taken together, the evolution of these forms illustrates how restructured linguistic subsystems (and eventually new varieties) emerge out of the interplay between inheritance and innovation." --