The papers of Edmund Bailey O'Callaghan (1797-1830), span the years 1830-1876, with the bulk of the material falling between 1845 and 1860. The papers consist of correspondence, a partial draft of O'Callaghan's History of New Netherland , lists, records, and bibliographical material.

O'Callaghan's diversified career as historian, bibliographer, legislator, physician, and journalist is only partially documented by this collection. After emigrating from Ireland in 1823, O'Callaghan became prominent in Canadian politics and was associated with the revolutionary party. At the same time he was active in the founding of the Society of the Friends of Ireland and was editor of the Montreal Vindicator . His political career in Canada reached its zenith when, in 1835, he was elected to the assembly of Upper Canada. His political career, however, was cut short by his participation in the Insurrection of 1837. With a reward offered for his capture, O'Callaghan found it expedient to flee to the United States. The Canadian phase of O'Callaghan's career is survived by only one document, but there are references to his activities in Canada in later correspondence, particularly with William Lyon MacKenzie.

O'Callaghan's first years in the United States were taken up with the practice of medicine and with editing the Northern Light , an industrial journal. Apparently in connection with the latter occupation, O'Callaghan had reason to examine the state records of New York. Finding a wealth of material among them, O'Callaghan embarked upon a new career as historian and bibliographer. In 1846 he published the first volume of his History of New Netherland . Despite financial losses on that volume, he came out with a second in 1849. The draft of volume two (books 4-6 and appendices) is present in his papers, as well as related correspondence.

As a result of this work O'Callaghan was commissioned to edit the Documentary History of the State of New York . A voluminous amount of correspondence concerning the collection of historical material on New York is contained in the collection. Additional correspondence deals with other bibliographic matters, with Americana rarities, editions of the Bible, and O'Callaghan's duties in the office of the secretary of state of New York.

Prominent correspondents include Solomon Alofsen, Edward G. Allen, Edward Armstrong, George Bancroft, Elizabeth T. Porter Beach, Theodric Romeyn Beck, John Romeyn Brodhead, John Carter Brown (1797-1874), Charles Deane, Samuel Gardner Drake, Lyman Copeland Draper, Thomas Ewbank, Édouard Raymond Fabre, Hector Fabre, F.-X. Garneau, William Gowans, Thaddeus William Harris, Samuel F. Haven, Charles J. Hoadly, James Lenox, George Livermore, William Lyons MacKenzie, Benj. N. Martin, Gregory Henry Moore, Henry Cruse Murphy, Francis Parkman, Louis Joseph Papineau, Louis Perrault, Charles Benjamin Richardson, John Gilmary Shea, Alpheus Todd, D. T. Valentine, Townsend Ward, and William A. Whitehead.