This subseries covers Adams's tenure as president of the Massachusetts Historical Society and primarily consists of correspondence. Topics include general society business, including research requests, membership, speakers, donations, and events; the controversy, media attention, and legal proceedings over the proposed development of MHS property on Hemenway Street; the Henry L. Shattuck wing; and the John F. Kennedy Medal for service to history. Frequent correspondents include Stephen T. Riley and Lyman H. Butterfield.

This subseries documents Adams's involvement in the Adams Memorial Society. Included are letters and invoices regarding landscaping and maintenance of the Adams Memorial in Washington, D.C., the Old House and other properties at Adams National Historic Site (later Adams National Historical Park), and Merrymount Park and other sites in Quincy, Massachusetts; society meetings and minutes; and the management of John Quincy Adams's library at the Boston Athenaeum. Frequent correspondents include Adams's cousin Mary Ogden Abbott and Wilhelmina Harris.

Diaries kept by Adams span primarily from 1950 to 1970. Common topics include daily life, leisure, recreation, and activities in Lincoln, Massachusetts, and the Glades; business trips and vacations, including trips to France, Europe, and the Bahamas; his work at the Sheraton Corporation and stock and bond trading with the Adams Securities Company; lunches and social clubs, including the Saturday Club, the Massachusetts Historical Society, the Tavern Club, and Phi Beta Kappa; raising children and his wife Ramelle's health; political opinions; poetry; and reading habits. Adams also describes attending a 1960 luncheon for Nikita Khrushchev and meeting John F. Kennedy on separate occasions.

Some entries are partially written in French and Greek. Financial notes and short stories are also occasionally intermixed with diary entries.

This subseries contains 11 volumes and mostly consists of unpublished short stories written by Adams for his children that are centered around a character named Ike and use historical figures from the Mayflower landing as characters. Other materials include a financial record and an idea journal.

This subseries contains separately arranged correspondence and includes letters dictated and received, loose and personal correspondence, and letters between Adams, Sommaripa, and campaign treasurer Henry B. Cabot, Jr. Common topics include endorsements, fundraising, and volunteer support. Files contain a mix of original correspondence, onionskin copies, and photocopies. Duplicated content may exist across multiple folders. Notable Adams supporters in correspondence include Cyrus S. Eaton, Ernest Gruening, Hudson Hoagland, Walter Lippmann, and Dr. Benjamin Spock.

Additional campaign correspondence exists in subseries III.B and III.C.

This subseries contains various files created by Thomas Boylston Adams and his campaign staff over the course of his 1966 campaign. Topics include advertisements and publicity, campaign office organization, management of staff and volunteers, the 1966 Massachusetts Democratic State Convention, the nomination process, platform and policy development, press releases and speeches, research material, and scheduling files, among others.

This series contains files created by campaign manager George Sommaripa and David Bird's consulting firm Bison Associates in the course of their work with Endicott Peabody and other Massachusetts political candidates.

The campaign financial papers primarily contain records from Adams's two campaign bank accounts, titled "Adams for Senate Campaign Committee" and "Thomas B. Adams" and both maintained by the Harvard Trust Company bank. Materials related to these accounts include checkbooks, checks, contribution lists, contribution schedules and bank deposit slips, and payroll records. Other files included are invoices and receipts, employee expense reporting, campaign financial status reports, lists of possible contributors, office purchases, and petty cash records. There are also invitations, RSVPs, and correspondence for a fundraising garden party in Lincoln, Massachusetts, and a luncheon held by the Overseas Press Club in New York City.

Some expense accounts and other materials originate with Abbie Hoffman, who worked for the Adams campaign in western Massachusetts.

This subseries contains newspaper clippings documenting Adams's Senate campaign, as well as his opponents Endicott Peabody and John F. Collins. Also included is one scrapbook of clippings. The scrapbook contains duplicates of many of the loose clippings.

This subseries includes correspondence generated during Adams's 1968 campaign. The majority of letters relate to fundraising and campaign contributions. Other topics include news media and publicity, his position on the Vietnam War, and personal thank you letters.

This subseries includes files created by Adams and his campaign staff over the course of his 1968 campaign. Topics include radio and newspaper advertising, scheduling, press releases, policy and platform development, notes and research for various statements, and staff memos, among others. Also included is a campaign diary.

This subseries includes bank records from Adams's 1968 campaign bank accounts, through the Newton-Waltham Bank and Trust Company. Materials related to these accounts include bank statements, deposits and contribution schedules, checkbooks, and checks. Other files include invoices and receipts, contributors and lists of names, petty cash records, and financial reports by treasurer John Bryant Paine, Jr., among others. There are also invitations, RSVPs, and a signed guest book for a fundraising party.

This subseries contains newspaper clippings documenting Adams's House of Representatives campaign, as well as the 1968 Democratic primary and overall 3rd District House race. Articles additionally relate to Adams's opponents Joseph G. Bradley and Philip J. Philbin.