URBAN REDEVELOPMENT.Nineteenth-century slum housing in the United States consisted of buildings with warrens of tiny, poorly ventilated rooms that resulted in a high incidence of infant mortality and infectious diseases among the European immigrant population. Reform movements began in 1901, with the New York State Tenement House Law and continued in the 1930s with zoning ordinances (intended to separate residential areas from the health-endangering waste products of industrial activities) and federal loans to build housing for workers who had fallen on hard times during the Great Depression.