This paper examines the relationship between public capital, specifically roads, and productivity in the United States from 1953 to 1989. It finds that vehicle-intensive industries benefit disproportionately from road-building, with productivity growth more significantly affected in these industries when road growth changes. The results suggest that causation runs from infrastructure to productivity, as road-building in the 1950s and 1960s provided a one-time boost to productivity levels. However, there is no evidence that roads offer an above-average return at the margin, and congestion significantly affects road services after 1973. The paper also explores the economic implications of congestion and the productivity of roads, finding that roads were highly productive before 1973 but not at the margin afterward. The results suggest that public investment may explain a substantial share of the productivity slowdown after 1973, but do not support the idea that roads offer an abnormal return at the margin. The paper concludes that the massive road-building of the 1950s and 1960s offered a one-time boost to productivity, rather than a continuing path to prosperity. The findings are consistent with simple network arguments and cost-benefit studies, and suggest that congestion becomes important after the interstate highway system was completed. The paper also highlights the importance of considering regional differences and the potential for bias in industry groupings. Overall, the results support the view that vehicle-intensive industries benefited disproportionately from road-building, but do not support the idea that roads offer an abnormal return at the margin.This paper examines the relationship between public capital, specifically roads, and productivity in the United States from 1953 to 1989. It finds that vehicle-intensive industries benefit disproportionately from road-building, with productivity growth more significantly affected in these industries when road growth changes. The results suggest that causation runs from infrastructure to productivity, as road-building in the 1950s and 1960s provided a one-time boost to productivity levels. However, there is no evidence that roads offer an above-average return at the margin, and congestion significantly affects road services after 1973. The paper also explores the economic implications of congestion and the productivity of roads, finding that roads were highly productive before 1973 but not at the margin afterward. The results suggest that public investment may explain a substantial share of the productivity slowdown after 1973, but do not support the idea that roads offer an abnormal return at the margin. The paper concludes that the massive road-building of the 1950s and 1960s offered a one-time boost to productivity, rather than a continuing path to prosperity. The findings are consistent with simple network arguments and cost-benefit studies, and suggest that congestion becomes important after the interstate highway system was completed. The paper also highlights the importance of considering regional differences and the potential for bias in industry groupings. Overall, the results support the view that vehicle-intensive industries benefited disproportionately from road-building, but do not support the idea that roads offer an abnormal return at the margin.