We study the contribution of economic conditions to the success of the first avowedly nativist political party in the United States. The Know-Nothing Party gained control of a number of state governments in the 1854-1856 elections running on a staunchly anti-Catholic and anti-Irish platform. Our analysis focuses on the case of Massachusetts, which had experienced a wave of Irish Famine immigration and was at the forefront of industrialization in the United States. Voters in towns with more exposure to Irish labor market crowdout and deskilling in manufacturing were more likely to vote for Know-Nothing candidates in state elections. These two forces played a decisive role in 1855, but not the other years of the Know Nothings’ success. We find evidence of reduced wealth accumulation for native workers most exposed to labor market crowdout and deskilling, though this was tempered by occupational upgrading.