This collection contains records and correspondence of the 3rd New York Cavalry Association, formed in Rochester, Monroe County, New York in June 1881. A majority of the letters were written in response to circulars sent out by the 3rd New York Cavalry Association announcing regimental reunions. There are 318 authors in this collection, of whom 274 were members, or representatives of members, of the 3rd Regiment of New York Cavalry. This represents about 12% of those who served in the 3rd New York Cavalry and survived the war.

Much of the correspondence is addressed to either Maurice Leyden, the president of the Association, or to Samuel Chase (S. C.) Pierce, the Association's secretary. It has been separated into two groups: Reunion Correspondence, which is organized by year and then alphabetically by author; and General Correspondence, which is organized alphabetically by author.

Reunion Correspondence, typically sent in response to invitations to each annual reunion, often provides news and updates from the authors. The letters often have manuscript annotations (probably by Leyden or Pierce) indicating whether the sender was planning to attend the reunion. General Correspondence includes queries or information about the whereabouts of regimental veterans, inquiries about Civil War pensions, and other business of the Association.

Reunion Records include copies of reunion circulars, rosters of attendees, a manuscript poem submitted to the 1902 reunion, a small number of bills and the treasurer's book.

General Records include a later history of the regiment and several miscellaneous documents and unmatched envelopes.