["Oxford Bulletin of Economics and Statistics, EarlyView. ", "\nABSTRACT\nThis paper examines long‐run unconditional convergence of labour productivity in manufacturing across 48 contiguous U.S. states. We construct a detailed panel data set of state‐industry pairs with over 120 industries covering the period 1880–2007. The remarkable finding is a rapid rate of unconditional β$$ \\beta $$‐convergence: 7.6% per year in the period 1880–2007, and about 6.5% in each period 1880–1940 and 1958–2007. We also find a steep rise in unconditional convergence from 5.5% in 1930–1940 to 10.6% in 1940–1947 and 9.4% in 1947–1958, followed by a considerable drop thereafter. In the years 1958–2007, the rate of convergence in ICT industries (8.3%) is higher than in 1st‐Industrial‐Revolution (6.3%) or 2nd‐Industrial‐Revolution (7.0%) industries. We interpret our results as a process of technological catch up between initially laggard Southern manufacturing and manufacturing industries in the North.\n"]