The records of the American Jewish Historical Society, the oldest national ethnic historical organization in the United States, include correspondence of officers and staff as well as inter-office memos, multiple versions of the constitution and by-laws of the society, meeting minutes of administrative branches and committees, membership and financial records, reports, exhibit materials, records relating to the society’s library and archival holdings, press releases and newspaper clippings, and publications and newsletters created by the society. There are also materials from various programs, such as meetings and conferences, tours, lectures, awards and dinners, films, and educational programs.

Hadassah Functions and Operations Records represent the bulk of aid and services provided to Hadassah's membership, from the 1920s to 2011. Materials found in the record group include correspondence, clippings, press releases, manuals and kits for chapters and members to implement programming and chapter structure, fundraising campaigns, scripts, study guides, programming for local and national meetings, biographical files, and training documentation. Departments documented in the record group include Public Affairs, Education, Women's Health, American Affairs, Zionist and International Affairs, Speakers Bureau, Fundraising, Program, Organization, Outreach and Tourism Departments. Materials related to the general administration of Hadassah are also in the record group; these materials include research and development of projects, archives department correspondence and other materials, Hadassah House administration, and strategic planning. The record group also documents Hadassah's efforts to expand membership outside of the United States, by the development of Hadassah International.

This collection contains the personal and professional papers of rabbi, Hebrew scholar, author, and editor Israel Elfenbein. These materials include correspondence with and relating to congregations, Hebrew periodicals, organizations, Elfenbein’s writings, personal correspondence, sermons, clippings, and manuscripts by Elfenbein and by other writers.

This collection contains the administrative records of the Hebrew Actors’ Union (HAU), the professional union of Yiddish theater performers, which was based in New York City. Materials include correspondence, membership materials, financial records and members’ dues information, meeting minutes, and a great deal of sheet music and play scripts of performances from the Yiddish theater. A majority of these performances were in New York City, but there are also materials from Philadelphia, Chicago, Boston, Toronto, and Montreal, as well as various locations in Israel and South America.

The records chronicle the ideology behind the Reconstructionist movement, the founding and activities of the Jewish Reconstructionist Foundation, and its growth and transformation from an ideology and movement into an established American Jewish denomination, Reconstructionist Judaism. The records also document two seminal figures in Reconstructionist Judaism, Mordecai Menahem Kaplan and Ira Eisenstein. Included in the collection are the administrative records of the Foundation (minutes, financial records, bylaws), publications produced by the Foundation including manuscript submissions for the influential publication The Reconstructionist, correspondence, sermons, prayer books produced by the Foundation, syllabi, sheet music, photographs, and speeches, among other material. In the correspondence are letters from Martin Buber, J. Edgar Hoover, and Albert Schweitzer.

The children and descendants of Isaac Mendes and Rachel Levy Seixas included individuals who had a great impact on communal affairs and colonial Jewish life in New York, Philadelphia, Newport, and Richmond. Though this collection does not preserve the total volume of papers produced by every family member, the documents contained herein demonstrate the importance of the family in both Jewish and secular life in late 17th and early 18th century North America.

The collection is valuable to researchers studying the Seixas family; civic, mercantile, and religious contributions of Jews in the colonial era; Jewish communities in New York, Philadelphia, Newport, and Richmond; the importance of religion to Colonial Jews; Jewish participation in the Revolutionary War, the War of 1812, and World War I; Jewish converts to Christianity; Jews as masons; and Congregation Shearith Israel of New York.

Prominent individuals in this collection include: Ephraim Hart, Grace Seixas Judah, Mrs. Jesse Judah, Israel Baer Kursheedt, Sarah Seixas Kursheedt, Hayman Levy, Nicholas Low, Isaac Moses, Naphtali Taylor Phillips, Benjamin Mendes Seixas, David G. Seixas, Gershom Mendes Seixas, Isaac Benjamin Seixas, Isaac M. Seixas, Jacob B. Seixas, Joshua Seixas, and Moses Mendes Seixas.

The collection includes: account records, books, circumcision instructions and register, correspondence, drawings, estate papers, a eulogy, family trees, legal documents, petitions, photographs, prayer books, a sermon, and shipping records.

This collection is arranged into four series: Series I: Family Papers; Series II: Moses Seixas (1744-1809); Series III: Gershom Mendes Seixas (1746-1816) and descendants; and Series IV: Benjamin Mendes Seixas (1748-1817) and descendants.

This collection contains correspondence, pamphlets, periodicals, newspapers, press releases, writings, clippings, brochures, fliers, and posters from the era of the Spanish Civil War, and later, documenting American and international fund-raising for humanitarian relief of Republican Spain; American and international public opinion about the war; the participation of Jews in the International Brigades; and reminiscences and commemorations of the war and, particularly, of the International Brigades, in later years. A portion of the material on relief work pertains to trade union activities, as documented in papers of Charles S. Zimmerman, of the International Ladies’ Garment Workers’ Union, in his capacity as leader of Trade Union Relief for Spain, in New York City. Other organizations represented include the Medical Bureau and North American Committee to Aid Spanish Democracy; the Spanish Information Bureau in New York; the Friends of the Abraham Lincoln Brigade; and the Israeli branch of the association of volunteers in the International Brigades. There are also autobiographical manuscripts by Benjamin Lubelski and Sigmund Stein, who participated in the International Brigades; and contemporary publications in a variety of languages, including publications of the anarchist-leaning Spanish trade union confederations CNT-FAI.