The Oral History of the American Left documents the broad range of experiences on the left, with a focus on underrepresented voices, particularly between 1910 and 1980. The Main Series (Series 1) is particularly sweeping in the topics that it documents, but a set of prominent topics emerge representing the interests of OHAL staff members in the early years of the collection. These include immigrant/ethnic radicalism, labor, women's history, radical newspapers, fraternal organizations, and student radicalism. The earliest interviews were done to collect the memories of men and women who could recall the 1910s-1920s. Later interviews document the effects of the Russian Revolution on the Left in the United States, the formation of social and cultural institutions by the "New Immigrant" groups, the history of socialism and anarchism, the relationship between the "Old Left" and "New Left," and Communist activism in the United States. There is also an analysis of the regional development of Left movements in the United States. OHAL interviewed representative figures from the Jewish, Finnish, Slovenian, Greek, Hungarian, Polish, Italian, Ukrainian, Lithuanian, African American, Japanese, Scandinavian, and Spanish Left. For many of these interviews, there is a focus on how ethnic identity and political identity interacted and how non-English-language presses and fraternal organizations preserved this identity in the United States. The cultural experiences of Yiddish-speaking Jews are particularly represented in this regard. Paul Buhle took a sizable amount of interviews related to the relationship between Yiddish-language literature and culture and Communist and socialist political organizations and newspapers.
The collection also documents the factionalism of the Left in the mid-20th century United States. Rank and file members and leaders alike comment on the conflicts between the Communist Party of the USA and different socialist and Trotskyist organizations, analyzing matters of theory and the personalities that drove the splits. The Johnson-Forest Tendency and CLR James receive particular attention. Other political parties/factions addressed include the the Socialist Party, Workers Party, Socialist Workers Party, and the American Labor Party. The CP's role in the period is examined in depth, both by members and opponents, especially during the 1930s. The interviews taken to support "Grandma Was an Activist" provide insight into the experiences of women activists during the period.
The collection includes several interviews with participants of the Abraham Lincoln Brigade, the US component of the International Brigades which fought in the Spanish Civil War. There are other interviews documenting the long tenure of Jasper McLevy, Socialist Party Mayor of Bridgeport, Connecticut from 1933-1957. Organizations discussed in other interviews include the Students for a Democratic Society (SDS), Workmens' Circle, International Labor Defense, National Lawyers Guild, the Southern Negro Youth Congress, and the Yidisher Kultur Farband (YKUF), among many others. The labor movement and the operations of different political parties and factions within labor unions are also frequently addressed. The International Ladies Garment Workers Union (ILGWU) and the needle trades are particularly well represented in this regard.
OHAL also received interviews from filmmakers and graduate students that were added to the collection as distinct units. These materials, found in Series 2-9, are further described at the series level.