Mothers' pensions were the first explicit welfare benefits established outside of poor relief in the United States. Contrary to established wisdom in political science, their enabling statutes spread very quickly across most states in the 1910s, with smaller, nonindustrial states often in the vanguard. Previous research concerning the predictors of state-level policy innovations has focused on a small subset of possible explanatory variables, typically economic or electoral conditions. We operationalize and test hypotheses about the influence of economic conditions, culture and ideology, electoral politics, governmental institutions and prior public policies, and the role of business, labor, and women's voluntary groups on the priority of state enactments. Our findings indicate that widespread federations of women's voluntary groups exerted a powerful influence on mothers' pension enactments even before most American women had the right to vote. We demonstrate the value to empirical political science of theories and variables referring to gender and women's politics.