According to historian James Grossman, "He reoriented the whole picture of the American story from the view that America was built on the spirit of the Wild West, to the idea that we are a nation of immigrants.

Their experience of religious persecution in Czarist Russia made them fiercely devoted to democracy and social justice (Handlin was a proto-"red diaper baby").

The couple owned a grocery store, the success of which along with real estate investments enabled them to send their children, Oscar, Nathan, and Sarah, to Harvard.

[11] Known for his prodigious memory that allowed him to attend classes without taking notes, in 1930, Handlin entered Brooklyn College at age 15, graduating in 1934, then earning a Master of Arts degree from Harvard University in 1935, after which he won a Frederick Sheldon Fellowship for research in Europe.

During his time as a graduate student at Harvard, Handlin was denied the position of vice president in the Henry Adams Club for being Jewish.

"[20] In 1947, he and his first wife Mary Flug Handlin published Commonwealth: A Study of the Role of Government in the American Economy: Massachusetts, 1774-1861, which revealed for the first time the importance of political action in the development of the US free enterprise system.

[11] Oscar Handlin argued that racism was a by-product of slavery, and that the main focus was on the fact that slaves, like indentured servants, were regarded as inferior because of their status, not necessarily because of their race.

[21] In 1964, Handlin published Fire Bell in the Night: The Crisis in Civil Rights, which criticized white supremacists and suburban liberals, but also criticized leftists for their Communist-inspired solutions such as quotas, school busing, and affirmative action, writing: "Preferential treatment demands a departure from the ideal which judges individuals by their own merits rather than by their affiliations.

"[citation needed] In March 1961, Handlin signed an ACLU-organized petition of scholars demanding that the House Committee on Un-American Activities (HUAC) cease operations.

"The study of the human past persuades me that, despite the frequent risks of failure, man has the capacity to make order and find purpose in the world in which he lives when he uses the power of his reason to do so."

His long-time colleague Bernard Bailyn noted Handlin's commitment to providing a historical perspective on policy issues:[23] He published widely on all the major public issues of the time: racism, group life, anti-Semitism, prejudice, the Bill of Rights, the business corporation, ethnicity, and the Jews and other groups in American society.

[citation needed] In December 1967, Handlin was one of 14 anti-Communist American scholars who co-wrote a report for the Freedom House Public Affairs Institute, which argued that disaster would strike if the US withdrew from Vietnam.