Kammala wannan jumla: Mangano ya halarci Makarantar Koyarwa ta Manual, New York Prep, da Kwalejin St. John. Shi memba ne na Phi Sigma Chi da kuma Kungiyar Abokan aiki. Da farko ya tafi aiki a gidan jana'izar mahaifinsa. A shekara ta 1934, an zabe shi a Majalisar Dokokin Jihar New York a matsayin dan Democrat, wanda ke wakiltar Gundumar 8 na Kings County. Ya yi aiki a cikin Majalisar a 1935, 1936, da 1937. Ya kasance wakili mai maye gurbin a cikin Babban Taron Kasa na Jam'iyyar Democrat na 1936, kuma zai yi aiki a matsayin wakili na 1940,
1956, 1960, da kuma 1964 Democratic National Conventions. A shekara ta 1937, an zabe shi Sheriff na Kings County. Ya yi aiki a matsayin Sheriff daga 1938 zuwa 1941. A shekara ta 1941, an zabe shi memba na Kwamitin Demokradiyya na Jihar New York. A cikin 1942, an soke matsayin Sheriff na County na Kings kuma an maye gurbinsa da ɗaya, sheriff na birni, yana mai da shi Sheriff na ƙarshe na County na Kings.