This series contains materials documenting participation in Irish American organizations, cultural expressions of Irish nationalism and republicanism, and other material collected by John T. Ridge. Materials in this series date from the mid-18th century to 2000, with the bulk of the materials dating from the late 19th century to the 1970s. The bulk of this series documents activities of the Ancient Order of Hibernians (AOH) divisions located in the greater New York City area as well as the national organization. AOH materials include photographs, convention proceedings, ledger books, and Hibernian Monthly Magazine. Other organizations represented include the County Cavan Society, County Tyrone Society, Friends of Irish Freedom, Irish Northern Aid, and the Loyal National Repeal Association. Other materials include day books of fire departments in New York City, biographies and histories relating to Irish history, Irish language grammar books, John Mitchel's radical Irish nationalist newspaper, The Citizen, sheet music, ephemera, correspondence, event programs, and newspaper and magazine clippings.

This series contains materials created or collected by Patrick Mullin during his time working with the Irish People newspaper. The New York-based publication was a weekly, volunteer-run paper that described itself as the "Voice of Irish Republicanism in America." It provided coverage and analysis of events in Ireland and America concerning conflict in Northern Ireland and more general British involvement in Ireland. In addition to meeting minutes, this series contains many of the publication's financial records, reflecting its relationship with Noraid (Irish Northern Aid) and other politically involved organizations.