Entrepreneurship is often found to be highly persistent over time. Although the historical roots of persisting effects of entrepreneurship are partially uncovered, their mechanisms remained largely unclear. To understand the historical roots of contemporaneous regional entrepreneurship, we exploit different types of historical self-employment in regions of Poland, a country that experienced different types of disruptive developments. In contrast to previous studies on other countries, we do not find a persistent effect of the general level of historical private sector self-employment. There is, however, a pronounced positive relationship between high regional levels of knowledge-intensive entrepreneurship in the 1920s and current start-up activity in general, even in areas where large parts of the local population were displaced after World War II. We find that the magnitude of this effect is independent of the mobility and an exchange of the local population. Our main conclusion is that the historical regional knowledge stock, as reflected by knowledge-intensive entrepreneurship, can be an important and stable historical root of modern entrepreneurship despite disruptive historical shocks and population discontinuities.