From 1945 to 1964, two-dozen states outside the South passed enforceable fair employment practice (FEP) laws. Yet some states passed such laws far earlier than others. Reviewing several bodies of research, I derive economic, political, institutional, and social hypotheses to explain their diffusion. Discrete-time, logit analysis of a newly assembled data set-containing both time constant and time-varying covariates-offer mixed support for most theories but strong support for theories stressing electoral politics. Wealth, political competition, and unified Democratic control are positively associated with the likelihood of passage, while percentage black is negatively associated with the likelihood of passage. I infer that Democrats were the party of fair employment in the urban North and that FEP laws passed earliest in politically competitive states in which whites did not perceive blacks as an economic threat. I conclude with suggestions for future research.