We craft a historically sensitive model of entrepreneurship linking individual actors to the evolving social structures they must navigate to acquire resources and launch new ventures. Theories of entrepreneurship and industry evolution suggest two opposing hypotheses: as an industry develops, launching a new venture may become more difficult for all but industry insiders and the socially prominent because of competition from large incumbents, or it may become easier for all people because the legitimacy accorded to the industry simplifies the entrepreneurial task. To test these two conflicting claims, we study the American magazine industry from 1741 to 1860. We find that magazine publishing was originally restricted to publishing-industry insiders, professionals, and the highly educated, but most later founders came from outside publishing and more were of middling stature. Gains by entrepreneurs from the social periphery, however, were uneven: most were doctors and clergy without college degrees in small urban areas; magazines founded by industry insiders remained predominant in the industry centers. Our analysis demonstrates the importance of grounding studies of entrepreneurship in historical context. It also shows that entrepreneurship scholars must attend to temporal shifts within the focal industry and in society at large.In a pioneering analysis, Stinchcombe (1965) proposed that entrepreneurial dynamics are influenced by historical conditions. Large-scale changes such as urbanization, the creation of new policy regimes, and technological breakthroughs may change the resources available to entrepreneurs, altering organizational founding rates by transforming the entrepreneurial task itself. Yet much research on entrepreneurship remains ahistorical. It assumes that the factors that make people more or less likely to create new organizations do not