He moved to Arizona with his family, where his father had a bandmaster position at Fort Whipple in the U.S. Army. La Guardia attended public schools and high school in Prescott, Arizona. After his father was discharged from his bandmaster position in 1898, Fiorello lived in Trieste. He graduated from the Dwight School, a private school on the Upper West Side of New York City.
La Guardia joined the State Department and served in U.S. consulates in Budapest, Trieste (Austria-Hungary, now Italy), and Fiume (Austria-Hungary, now Rijeka, Croatia), (1901–1906). He returned to the United States to continue his education at New York University. From 1907 to 1910, he worked as an interpreter for the U.S. Bureau of Immigration at the Ellis Island immigration station.
As the son of Italian immigrants and an interpreter on Ellis Island between 1907 and 1910, La Guardia had experienced how immigration policies affected the families that came to the United States. He wanted a change for the immigrants, especially with the immigrant medical examinations that took place on Ellis Island. His passion for justice among immigrants, and his ability to speak Italian, Yiddish, and Croatian helped him in his endeavor for justice amongst immigrant factory workers and set him on his path in public Service.
He graduated from New York University School of Law in 1910, was admitted to the bar the same year, and began a law practice in New York City.
Never an isolationist, he supported using American influence abroad on behalf of democracy or for national independence or against autocracy. Thus he supported the Irish independence movement and the anti-czarist Russian Revolution of 1917, but did not approve of Vladimir Lenin. Unlike most progressive colleagues, such as Norris, La Guardia consistently backed internationalism, speaking in favor of the League of Nations and the Inter-Parliamentary Union as well as peace and disarmament conferences. In domestic policies he tended toward socialism and wanted to nationalize and regulate; however he was never close to the Socialist Party and never bothered to read Karl Marx.
In 1919, La Guardia was chosen to run as the Republican candidate for the office of President of the New York City Board of Aldermen. His Democratic opponent was Robert L. Moran, an alderman from the Bronx who had succeeded to the Board presidency in 1918 when Alfred E. Smith, who had been elected board President in 1917, became governor. Michael "Dynamite Mike" Kelly, commander of New York's Third "Shamrock" Battalion, also joined the race. Tammany Hall looked with alarm upon Kelly's entrance into the campaign and tried to persuade him to withdraw his candidacy and throw his support behind Moran. When he refused, Tammany went to the New York Supreme Court and successfully sued to keep Kelly's name off the ballot. When Election Day arrived, over 3,500 of Kelly's supporters wrote Kelly's name on the ballot. This number was sufficient to defeat Moran, who lost to La Guardia by 1,363 votes.
As a Republican, La Guardia had to support Harding in 1920; he had to be silent in the 1928 campaign although he favored Al Smith, a Democrat. In 1929, he lost the election for mayor to incumbent Democrat Jimmy Walker by a landslide. In 1932 he was defeated for re-election to the House by James J. Lanzetta, the Democratic candidate; 1932 was not a good year for Republican candidates like La Guardia, and the 20th Congressional district was shifting from a Jewish and Italian-American population to a Puerto Rican population. However, it has also been argued that powerful Tammany Hall boss Jimmy Hines was able to successfully get enough votes forged to get La Guardia unseated in this election as well.
La Guardia was the city's first Italian-American mayor, but was not a typical Italian New Yorker. He was a Republican Episcopalian who had grown up in Arizona and had a Triestine Jewish mother and a lapsed Catholic father. He spoke several languages, reportedly including Hebrew, Croatian, German, Italian, and Yiddish. It served him well during a contentious congressional campaign in 1922. When Henry Frank, a Jewish opponent, accused him of anti-Semitism, La Guardia rejected the suggestion that he publicly disclose that his mother was Jewish as "self-serving". Instead, La Guardia dictated an open letter in Yiddish that was also printed in Yiddish. In it, he challenged Frank to publicly and openly debate the issues of the campaign "ENTIRELY IN THE YIDDISH LANGUAGE." Frank, although he was Jewish, could not speak the language and was forced to decline—and lost the election.
La Guardia, a Republican who appealed across party lines, was very popular in New York during the 1930s. As a New Dealer, he supported President Franklin D. Roosevelt, a Democrat, and in turn Roosevelt heavily funded the city and cut off patronage for La Guardia's enemies. La Guardia revitalized New York City and restored public faith in City Hall. 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 employment on merit in place of patronage jobs. La Guardia is also remembered for his WNYC radio program "Talk to the People," which aired from December 1941 till December 1945.
La Guardia, running as a Republican, won a seat in Congress from the Italian stronghold of East Harlem in 1922 and served in the House until March 3, 1933. A leading liberal reformer, La Guardia sponsored labor legislation and railed against immigration quotas. His major legislation was the Norris–La Guardia Act, cosponsored with Nebraska senator George Norris in 1932. It circumvented Supreme Court limitations on the activities of labor unions, especially as those limitations were imposed between the enactment of the Clayton Antitrust Act in 1914 and the end of the 1920s. Based on the theory that the lower courts are creations not of the Constitution but of Congress, and that Congress therefore has wide power in defining and restricting their jurisdiction, the act forbids issuance of injunctions to sustain anti-union contracts of employment, to prevent ceasing or refusing to perform any work or remain in any relation of employment, or to restrain acts generally constituting component parts of strikes, boycotts, and picketing. It also said courts could no longer enforce yellow-dog contracts, which are labor contracts prohibiting a worker from joining a union.
He was an outspoken and early critic of Adolf Hitler and the Nazi regime. In a public address in 1934, La Guardia warned that "part of Hitler's program is the complete annihilation of the Jews in Germany". In 1937, speaking before the Women's Division of the American Jewish Congress, he called for the creation of a special pavilion at the upcoming New York World's Fair, "a chamber of horrors" for "that brown-shirted fanatic". He also encouraged the boycotting of German goods, led anti-Nazi rallies, and promoted legislation to facilitate the U.S. rescue of the Jewish refugees.
Known for his love of music, La Guardia was noted for spontaneously conducting professional and student orchestras and was instrumental in the creation of the High School of Music & Art in 1936, now renamed the Fiorello H. LaGuardia High School of Music & Art and Performing Arts.
Responding to popular disdain for the sometimes corrupt City Council, La Guardia successfully proposed a reformed 1938 City Charter that created a powerful new New York City Board of Estimate, similar to a corporate board of Directors.
1939 was a busy year, as he opened the 1939 New York World's Fair at Flushing Meadows-Corona Park, Queens, opened New York Municipal Airport No. 2 in Queens (later renamed Fiorello H. LaGuardia Field), and had the city buy out the Interborough Rapid Transit Company and Brooklyn–Manhattan Transit Corporation, thus completing the public takeover of the subway system. When the city's newspapers were closed by a strike he famously read the comics on the radio.
In 1941 during the run-up to American involvement in World War II, President Roosevelt appointed La Guardia first Director of the new Office of Civilian Defense (OCD). Roosevelt was an admirer of La Guardia; after meeting Winston Churchill for the first time he described him as "an English Mayor La Guardia". The OCD was the national agency responsible for preparing for blackouts, air raid wardens, sirens, and shelters in case of German air raids. The government knew that such air raids were impossible but the goal was to psychologically mobilize many thousands of middle class volunteers to make them feel part of the war effort. La Guardia remained Mayor of New York, shuttling back and forth with three days in Washington and four in the city in an effort to do justice to two herculean jobs. On top of this, he still performed other gestures, such as arranging police protection with his personal assurances for local artists Joe Simon and Jack Kirby, when they were threatened by Nazi supporters for their new patriotic comic book superhero, Captain America. After the attack on Pearl Harbor in December 1941, his role was turned over to full-time Director of OCD, James M. Landis. La Guardia's popularity slipped away and he ran so poorly in straw polls in 1945 that he did not run for a fourth term.
Unemployment ended, and the city was a gateway for military supplies and Soldiers sent to Europe, with the Brooklyn Navy Yard providing many of the warships and the garment trade providing uniforms. The city's great financiers, however, were less important in decision making than the policy makers in Washington, and very high wartime taxes were not offset by heavy war spending. New York was not a center of heavy industry and did not see a wartime boom, as defense plants were built elsewhere. FDR refused to make La Guardia a general and was unable to provide fresh money for the city. By 1944 the city was short of funds to pay for La Guardia's new programs.
La Guardia was the Director general for the United Nations Relief and Rehabilitation Administration (UNRRA) in 1946.
He died of pancreatic cancer in his home at 5020 Goodridge Avenue, in the Riverdale section of The Bronx on September 20, 1947, aged 64 and is interred at Woodlawn Cemetery in The Bronx, New York City.
In 1972 the United States Postal Service honored La Guardia with a 14-cent postage stamp.
La Guardia was ranked first among the nation's mayors in a 1993 poll of historians and social Scientists. According to biographer Mason B. Williams, his close collaboration with Roosevelt's New Deal proved a striking success in linking national money and local needs. La Guardia enabled the political recognition new groups that had been largely excluded from the political system, such as Jews and Italians. His administration (in cooperation with Robert Moses) gave New York its modern infrastructure. His far-sighted goals raised ambitions for new levels of urban possibility. According to Thomas Kessner, trends since his tenure mean that "people would be afraid of allowing anybody to take that kind of power".
La Guardia was a fictionalized character in many films – in Ghostbusters II La Guardia's ghost talks to New York Mayor Lenny (played by David Margulies). He was also the subject of the hit Broadway musical Fiorello!, portrayed by actor Tom Bosley and in The Little Flower, portrayed by Tony Lo Bianco. Fiorello! won a Pulitzer Prize, and ran for two years (1959–1961).