 As a Representative, La Guardia represented an ethnically diverse slum district in East Harlem and, although barred from important committee posts because of his political independence, he was a tireless and vocal champion of progressive causes.La Guardia took office on March 4, 1917, but soon was commissioned into the United States Army Air Service; he rose to the rank of major in command of a unit of Ca.44 bombers on the Italian-Austrian front in World War I.He resigned his seat in Congress on December 31, 1919.