Two types of explanations of state government innovation have been proposed: internal determinants models (which posit that the factors causing a state government to innovate are political, economic, and social characteristics of a state) and regional diffusion models (which point toward the role of policy adoptions by neighboring states in prompting a state to adopt). We show that the two are conceptually compatible, relying on Mohr's theory of organizational innovation. Then we develop and test a unified explanation of state lottery adoptions reflecting both internal and regional influences. The empirical results provide a great degree of support for Mohr's theory. For the empirical analysis, we rely on event history analysis, a form of pooled cross-sectional time series analysis, which we believe may be useful in a wide variety of subfields of political science. Event history analysis may be able to explain important forms of political behavior (by individuals, organizations, or governments) even if they occur only rarely.