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As the United States grew rapidly and urbanized between 1870 and 1930, nonfarm residential construction and home mortgage debt became increas-ingly important to the nation’s capital formation, Wnancial structure, and short- run aggregate performance. However, both activities remained highly localized, institutionally diverse, and unevenly regulated during this period. As a result, residential construction and mortgage credit were poorly mea-sured and largely unexamined before 1930. This all changed during the Great Depression when the federal government responded to the worst housing and mortgage crisis in the nation’s history with a Wve- year burst of regulatory initiatives. Some of these were temporary, emergency interven-tions, while others permanently transformed the nation’s homebuilding and residential mortgage lending sectors. These interventions created a more institutionally mature and integrated national housing market, and provided new sources of data and opportunities for research. The National Bureau of Economic Research (NBER) played a centra