During his terms , he unified the transit system , directed the building of low-cost public housing , public playgrounds , and parks , constructed airports , reorganized the police force , defeated the powerful political machine Tammany Hall and improved employment rates in New York City , even during the depression . He unified the transit system ; directed the building of low-cost public housing , public playgrounds , and parks ; constructed airports ; reorganized the police force ; defeated the powerful Tammany Hall political machine ; and reestablished merit employment in place of patronage jobs .