There are two groups of correspondence. The first group covers the period 1774 to 1978 and is arranged chronologically. The earliest letters are written by James W. Foster (1807-1866) to his wife while he was serving in the Virginia General Assembly in Richmond. There are also letters written by John S. Knox, Sr. (1827-1906) in Alexandria to his wife. There are Civil War letters written by David Holmes Conrad (1800-1877) of Martinsburg, (West) Virginia to James W. Foster (concerning the deaths of his sons Holmes Addison Conrad (1837-1861) and Henry Tucker Conrad (1839-1861), while they were serving with the 2nd Virginia Infantry at Manassas. There are also letters from Dr. Arthur Moray Randolph (1815-1867) of Tallahassee, Florida regarding the death of his son Thomas Easton Randolph (1841-1862) of the 1st Florida Infantry. The other Civil War letters are written by Thomas Hunton Foster (1835-1864) to his father while he was a prisoner of war at Point Lookout, Maryland. There is a 1902 letter from Eppa Hunton (1822-1908) containing comments on his son's law practice and attendance at the Constitutional Convention in Richmond. There is a good deal of correspondence to and from Turner Foster and his brother E. Carter Foster (1895-1973) while they were attending Episcopal High School in Alexandria, and while Turner Foster was attending Bogue Institute in Indianapolis, and Hatfield Institute in Chicago. Finally, this group contains letters written while Turner Foster was employed in thrashing and harvesting jobs out West in Colorado, Kansas, Minnesota, New Mexico, and Oklahoma. There are also postcards written by him during this period in the Subject Files.

The second group of correspondence covers the years 1930 to 1972 and is arranged by year (with some gaps), and thereunder alphabetically by surname or topic. This group concerns mainly to the operation of Glenville Farm. It contains correspondence, as well as accounts and receipts, pertaining to seed, fertilizer, feed, coal, gas, and oil, livestock and equipment purchases, sales, and repairs, warranty information, hiring of farm hands, stock purchases and dividends, vestry and financial information relating to Grace Church, insurance and taxes, and other matters. There is a good deal of correspondence from the Department of Agriculture, the Virginia Aberdeen-Angus Association, the Fauquier National Bank of Warrenton, and information on various speech classes and institutes. Finally, there are many letters between Foster and his siblings concerning the settlement of their mother's estate and the sale of Glenville.

The majority of the financial records are bills and receipts that are arranged by year, and thereunder alphabetically by company name or type of product purchased. Included are records for livestock purchases and registrations, hardware and building materials, clothing and general merchandise, feed, seed, and fertilizer, vehicles and equipment repairs, insurance premiums, veterinary services, telephone and electric bills, periodical subscriptions and membership dues, and payments for work by farm hands. This series also contains numerous account books, check stub books, farm and personal account books, ledgers, day books, tax tickets and receipts, as well as personal accounts and receipts (1919-1923) of Mrs. James R. Foster. There are also financial statements and annual reports of various corporations in which Foster owned stock, including AT&T, Coca-Cola, Eastman Kodak, General Motors, General Electric, Procter and Gamble, RCA, Standard Oil, and U.S. Steel. They date from the mid-1920's to mid-1930's. Also included in this series are annual statements of Glenville Farm (1925-1952 and 1966), which detail receipts and disbursements, and yearly expenses, including livestock bought and sold, crops sold, fertilizer and seed purchases, gas and kerosene purchases, repairs and improvements, wages paid, money borrowed, equipment purchases, taxes, veterinary services, and other expenses relating to the maintenance of Glenville Farm.

The subject files include Bible records, books, certificates, clippings, deeds, and diaries, including reminiscences, written by Foster in 1968, of his time employed as a harvest hand out West in 1919. The subject files also contain Episcopal High School memorabilia, estate papers, a framed pencil drawing of Lucelia Hunton Foster (1811-1888), historical notes on the Civil War and Glenville, genealogical notes on the Carter, Foster, and Turner families, guardians' accounts, insurance papers, invitations, memorandum books, photographs and photograph albums, obituaries, copies of "The Parish Leaflet" for Piedmont and Whittle Parishes, plats and surveys, postcards, scrapbooks, and other items.

Turner Foster served as a member of the Scott District Road Board. The records cover the period from 1923 to 1927, and include budgets, correspondence (a good deal of it is with the Board's chairman Thomas B. Glascock), minutes, petitions, road workers' accounts, pay rolls, and expense accounts, relating to condition, maintenance, improvements, and construction of roads in Fauquier County.

The Millard Institute of Normal Speech records detail Foster's establishment and operation of a branch of the Institute in the basement of the Fauquier County courthouse. Foster had attended the Institute, located in Milwaukee, Wisconsin, and was impressed by its teaching methods and the treatment he received. The files contain class exercise notebooks, contracts, correspondence, financial records, a card file of prospective students, and a copy of "The Millard Instructor - A Key to Perfect Speech" by Lee Wells Millard.