AbstractMore than 30 million people migrated to the USA between late-ninetieth and early-twentieth century, and thousands became inventors. Drawing on a novel dataset of immigrant inventors in the USA, we assess the city-level impact of immigrants’ patenting and their contribution to the technological specialization of the receiving US regions between 1870 and 1940. Our results show that native inventors benefited from the inventive activity of immigrants. In addition, we show that the knowledge transferred by immigrants gave rise to new and previously not exiting technological fields in the US regions where immigrants moved to.