Abstract: Did migrants help make Paris a Mecca for the arts and Vienna a beacon of classical music? Or was their rise a pure consequence of local actors? Here, we use data more than 22,000 famous historical individuals born between the years 1000 and 2000 to estimate the contribution of famous immigrants, emigrants, and locals to the knowledge specializations of European regions. We find that the probability that a region develops a specialization in a new activity (physics, philosophy, painting, etc.) grows with the presence of immigrants with knowledge on that activity and related activities, while the opposite holds for loosing existing specializations. In contrast, we do not find robust evidence that locals with related knowledge play a statistically significant role in entries or exits. We address some of the endogeneity concerns using highly restrictive fixed-effects models considering any location-period-activity specific factors (e.g. the presence of a new university attracting scientists).