The Lefferts Family series contains personal and business documents created by or in regards to members of the Lefferts family and families closely related to the Lefferts through marriage or business. These related families include the Cortelyou, Vanderbilt, Lott, Smith, Nostrand, Ditmars, Vecht and Remsen families of Brooklyn. Many of the prominent Lefferts family members are included in this series. Date spans of the lives of each figure have been provided where possible so as not to confuse the figures with other family members with the same name.

These documents include some of the early land grants and indentures maintained by the Lefferts family. Among these are the original land grant from Peter Stuyvesant to Pieter Janse Hagewout in 1661 and the records of his great-grandson, Peter Lefferts. Among Peter's files is an account of items and expenses for his funeral. Among the papers of his wife, Femmetie Hegeman, is the deed and land grant from Peter Stuyvesant to Adriaen Hegeman. Part of this land eventually passed to Femmetie and would become part of the Lefferts farm after her marriage to Peter. The papers of Peter's father, John Lefferts (1719-1776), includes an inventory of his estate taken in 1778 and provides an account of items the Lefferts had closest to the burning down of the Lefferts home in 1776. The files on Gertrude Lefferts Vanderbilt include accounts of her experiences on the family farm during the 1863 Draft Riots including aiding and sheltering black Americans who had fled from Manhattan. These files also include a manuscript titled "Incidents in the home life during the War of the Revolution" containing recollections of the family's oral history in regards to the Battle of Long Island. A folder on John Cortelyou (1772-1855) includes many documents on his care after he was declared "A Lunatic". John Lefferts was appointed to oversee Cortelyou's estate.

The series also includes some business and legal records related to the Lefferts family and other historic Brooklyn families. This includes some slave bills and indentures, land transfers, estate claims by members of the Ditmars and Vechte families, and the title for the Remsen family farm. An account book of Jacobus Lefferts is also within this series. Jacobus Lefferts was a wealthy farmer in the town of New Utrecht and the account book includes the names of over 60 persons with whom he dealt, mostly also in New Utrecht. For additional documents regarding businesses owned and operated by the Lefferts or documents on the operation of the Lefferts farm, see Series 2: Lefferts Businesses.

The Lefferts Businesses series contains documents related to the operation of several businesses which the Lefferts family ran or had an interest in. The majority of the materials in this series concern transportation infrastructure companies that operated in Brooklyn such as the Jamaica and Flatbush Turnpike Company, the Gravesend and Coney Island Bridge and Road Company and the Brooklyn, Flatbush, and Coney Island Railway Company. Many of these companies were involved in creating the early transportation infrastructure of Kings County some of which is still used today. The Jamaica and Flatbush Turnpike, for example, is one of the oldest roads in Kings County. The materials include receipts, account ledgers, stock and bond certificates, and indentures. The series also contains some receipts and other records concerning the operations of the Lefferts farm and other official business carried out by the Lefferts family in Brooklyn. More materials related to Lefferts businesses and accounts can be found in the Lefferts Family series, particularly material related to the Lefferts farm, tenants, land acquisitions and transfers.

The Lefferts House and Ephemera series consists of materials which are specifically related to the upkeep and functioning of the Lefferts Historic House Museum, items accumulated by the museum with no immediately clear connection to Lefferts family members, and other ephemera from the collection.

The Household Goods Inventories give accounts of furniture, textiles, and other three dimensional objects which were part of the Lefferts house prior to its move to Prospect Park. The "General Small Items" and "Manuscripts and Poems" are all items which were between the pages of Lefferts books or mixed in with other Lefferts documents without credit to their source. This series also holds some items connected to the Lefferts outside of the Lefferts Historic House Museum. The brochure on "Brookwood" refers to once Virginia home of Mary Gray Lefferts and the report from the Lefferts Manor Association refers to association of the landmarked area within the Prospect-Lefferts Gardens neighborhood of Brooklyn. This series also includes some hand-written recipes used by Cornelia Stuyvesant. More recipes can be found in the cookbooks in the Books and Scrapbooks series.

The Genealogical Material series includes records of births, deaths, and marriages that are among the Lefferts family materials. The majority of the materials are related to the Lefferts family and its branches including some members of the Cortelyou, Lott, Vanderbilt, Van Pelt, Haughwout, Lloyd, and Hegeman families. Some of these lists were taken from loose pages inserted into the Lefferts family Bibles but there is also a book including a chart genealogy of eight generations of the Lefferts-Haughwout family and the visually impressive Marshall Lefferts family tree circle genealogy.

Most of the material in the series is related to the above-mentioned Brooklyn families but there is also Reverend Dr. Schoonmaker's Book of Marriages and Baptisms which includes a listing of many others who were baptized or married in Brooklyn.

Some genealogical notes of births and deaths may be remain on the flyeaves not pulled from some of the books in the Books and Scrapbooks series. The Books and Scrapbooks series also includes a copy of Teunis G. Bergen's Genealogy of the Lefferts family, 1650-1718.

The Maps series contains eight different maps including maps that are clearly related to the Lefferts family and those that are not. Of particularly note is the broadside advertisement for the sale of land owned by John Lefferts (1826-1893) in Flatbush. Two versions of this map are included, one unmarked and one marked with "Sold" stamps in some of the 500 lots that were for sale. Several other surveyor maps are included in the series, though two include unknown areas. Also included is a map related to the Battle of Long Island detailing the position of the troops of British General James Grant.

The Graphic Materials series contains images of a variety of subjects related to the Lefferts family, the Lefferts house, Brooklyn, New York City, and New York State. The genre of materials includes photographic prints, tintypes, daguerreotypes, glass plate negatives, photo albums, picture postcards, and prints of engravings. The series does not include maps or scrapbooks which can be found in Series 5: Maps and Series 8: Books and Scrapbooks respectively. The series has been broken down into three sub-series: Sub-Series 1: Lefferts Graphic Materials, Sub-Series 2: Brooklyn and New York Graphic Materials, and Sub-Series 3: Other Graphic Materials. See the individual scope notes below for each sub-series for descriptions.

The Clippings series contains newsprint articles collected by the Lefferts family or on topics relevant to the Lefferts family and the Lefferts house. The majority of the materials are from the mid to late 19th Century and concern topics that include Brooklyn, the Civil War, Slavery, and retrospectives on the Battle of Long Island. The collection also contains the newsletters "The Forest Leaf" and "The Melodeon" which were produced for social service benefit purposes following the Civil War. Clippings from the 20th Century primarily concern the Lefferts house, the archaeological work associated with it, its eventual move to Prospect Park in 1918, and the place of the Lefferts family and house in early New York Dutch history. There are also early 20th Century articles on World War I and the assassination of President William McKinley.

The Books and Scrapbooks series contains a variety of books which were either created by or maintained by the Lefferts family or acquired by the attendants of the Lefferts Historical House Museum. Books were kept within the collection if they had a strong connection to the Lefferts family or the Lefferts Historical House, if they had a strong connection to the life of the Lefferts particular to colonial American history, or if they included important inscriptions, marginalia, or notations and correspondence.

There are a variety of religious books and bibles within the series including four very large bibles. Three of these bibles are in Dutch and date from the mid-17th Century to the mid-18th Century. The oversized Dutch Bibles are published by Hendrick and Jacob Keur and the oversized English Bible is published by Benjamin Kennicott. These family bibles were likely important pieces of the Lefferts household and many included handwritten accounts of family births, deaths, and marriages. Many of these documents have been moved to the Genealogical Material series but the Dutch Keur Bible from 1741 still includes some inscriptions of Cowenhoven family and Lefferts family births and deaths. In addition to the large family bibles, there are also several editions of the small Het Nieuwe Testament. The Reformed Dutch Church of Flatbush pointed out in its "Quarter Milllennial Anniversary" booklet (1904) that "it is probable that all the Dutch families own one or more of these books still" indicating the importance of this New Testament in Dutch to the religious families of Flatbush with Dutch heritage even into the 20th Century.

There are some cookbooks and housekeeping guides included in this series. Most notable of these is the handwritten cookbook that was likely compiled by Maria Lott Lefferts and Gertrude Lefferts Vanderbilt. This cookbook also contains a loose page of recipes and some sewing threads that were left inside the book. Some of the printed cookbooks also contain handwritten recipes in the margins. The Receipts donated by the members of Saint Anna's Chapter of Saint Paul's Church in the Village of Flatbush includes a handwritten recipe for "Mother's Muffins" (page 42) and Housekeeping in old Virginia: Containing contributions from two hundred and fifty ladies in Virginia includes a handwritten recipe for "Sweet Pickled Fruit." Some more recipes, these used by Cornelia Stuyvesant, can be found in the Lefferts House and Ephemera series.

Other notable books in the series include the arithmetic workbook of Maria Lott Lefferts, a scrapbook belonging to the Alexander family containing an assortment of collected and hand-drawn book and advertisement designs, the rare Batavische Arcadia by Johan van Heemskerk (1662), and several old-Dutch religious books from the 17th and 18th Centuries.