Correspondence (alphabetical) consists of correspondence written to Teunis G. Bergen that was culled from his office records. Documents in this series are arranged alphabetically according to the name of the correspondent. The bulk of the correspondence concerns Bergen's duties as Supervisor of New Utrecht. In addition, there are letters requesting his expertise in matters of genealogy, history, and surveying, as well as invitations to civic, social, and political events.

Financial records comprises documents pertaining to Bergen's personal finances, including account ledgers; bank books; bank, tax and business receipts; property deeds; expenditure books; bank checks; etc.

Genealogical research primarily consists of the research materials compiled by Bergen to write his book, The Bergen Family: Or the Descendents of Hans Hansen Bergen, One of the Early Settlers of New York and Brooklyn, L.I. Correspondence in this collection consists of responses of Bergen extended family members concerning birth, marriage, and death dates. The miscellaneous folders contain research materials from a variety of sources and includes what appear to be drafts of his book. The folders titled with geographic place names consist of research materials pertaining to branches of the Bergen family in relation to the areas in which they settled. Also included are items related to the genealogy of other prominent Brooklyn families. The Coats of Arms folder contains coats of arms of the Schenck, Van der Veer, Lott, Cowenhoven, Voorhies, and Van Duyn families. The Schenck family correspondence consists of letters to Bergen from members of the Schenck family of Brooklyn requesting information on their family's genealogy. These letters highlight Bergen's role in his community as an expert on local history and genealogy.

History of New Utrecht is organized into three subseries. Bound volumes consists of bound copies of Teunis G. Bergen's seven-volume work, A History of New Utrecht, Long Island, Chapter drafts consists of handwritten drafts of the book's chapters, and New Utrecht records comprises records concerning the history of New Utrecht. Included in the records are the abstracts of land deeds of New Utrecht residents dating back to the 17th century; brief narrative histories of the Methodist, Episcopal, and Dutch Reformed churches of New Utrecht; a list of constables of New Utrecht dating back to the 17th century; local election records from 1849 to 1858; translations of Dutch records from the town of New Utrecht by Bergen, including issues of the Brooklyn Eagle in which some translations were published; records of various New Utrecht civic offices; etc.

Kings County Board of Supervisors comprises documents produced by Bergen during his tenure representing the town of New Utrecht on the Kings County Board of Supervisors. The papers in this series consist of handwritten drafts of laws and ordinances, petitions, requests to the New York State Legislature, and meeting minutes. These documents provide a glimpse into Bergen's role as Supervisor of New Utrecht, as well as some of the political, social, and legal issues of concern during his tenure on the Board.

Personal Papers includes Bergen's childhood school books, legal documents, travel logs, and other ephemera. The correspondence files in this series document many aspects of Bergen's life, including his appointments to the New Utrecht Board of Supervisors, as Commissioner of Records, and to the United States Congress; invitations to various civic functions; requests for land surveying; and correspondence with local residents about farming. The deeds, leases, and mortgages in this series document Bergen's land transactions in New Utrecht. Additionally, the series contains papers pertaining to Bergen's military service, as well as documents concerning the New York State Constitutional Conventions of 1846, 1854, and 1860.

Surveying records is organized into seven subseries and documents the various duties carried out by Teunis G. Bergen as a surveyor. The series is comprised primarily of maps and surveys of land owned by residents of Brooklyn and its environs, as well as roads and streets in the area, providing a glimpse into the evolution of Brooklyn's geography and physical infrastructure in the mid-to-late 19th century. Also included are drafts of legal documents, including deeds and legal land descriptions; building specifications of houses in Brooklyn; notes and calculations recorded by Bergen in the course of his surveying work; and title searches undertaken by Bergen to support his surveying work. The series is organized into seven subseries: Bound surveys; Drafts of legal documents; Field notes and calculations; Maps and surveys; Map tracings and land descriptions; Specifications of houses; and Title searches. Subseries 1 is comprised of five bound and numbered volumes, arranged in numerical order. Subseries 2, 3, 5, 6, and 7 are arranged alphabetically according to the personal name of a propert owner or the property's name. Subseries 4 is organized alphabetically by neighborhood name, and thereafter by the property owner's name.

Bergen family papers comprises various papers of Teunis Bergen's family members. Of particular interest is a folder of Bergen family land records dated 1696-1700, including maps of Hans Hansen Bergen's land. Also included are papers pertaining to Teunis G. Bergen's father, Garret Bergen; his first cousin once removed, Cornelius Bergen; his wife, Jane Bergen; his younger cousin, John C. Bergen; his brother, Peter G. Bergen; and his son, Garret T. Bergen. The types of records include school papers, certificates of appointment to civil and military appointments, land deeds, mortgages, as well as a bill of sale for a slave once owned by Cornelius Bergen.

Bergen extended family papers is organized into three subseries and primarily concerns family genealogies and family members' estates. Conover/Cowenhoven family papers comprises legal documents and correspondence between Bergen and various members of the Conover and Cowenhoven families. Included are the estate papers of Johanna Conover (Bergen's first cousin), as well as Elizabeth and Phebe Cowenhoven. The documents reveal that Bergen was named executor of all three of these estates. Also included are letters from Conover family members, including George S. Conover, President of the town of Seneca, New York (1873-1875). Cortelyou family papers consists of correspondence between Teunis G. Bergen and various members of the Cortelyou family, primarily concerning Cortelyou genealogy. Included are letters from his son-in-law, Peter L. Cortelyou, the last wills and testaments of Mary and Maria Cortelyou, and deeds and abstracts of Cortelyou family land holdings. Wyckoff family papers consists primarily of correspondence between Teunis G. Bergen and members of his wife's family, the Wyckoffs. It also includes documents pertaining to the estate and last will and testament of Peter Wyckoff.