Prisoners employed in manufacturing constitute 4.2% of total U.S. manufacturing employment in 2005; they produce cheap goods, creating labor demand shock. I study the economic externalities of convict labor on local labor markets and firms. Using newly collected panel data on U.S. prisons and convict-labor camps from 1886 to 1940, I calculate each county's exposure to prisons. I exploit quasi-random variation in county's exposure to capacities of pre-convict-labor