The 1st Regiment Massachusetts Volunteer Heavy Artillery Association Records includes by-laws, correspondence, rosters, record books, member surveys, sketchbooks, journal transcripts, and newspaper clippings. The collection has been arranged into two series.

Series I. Administrative Records includes by-laws, constitution articles, record books of meeting minutes, correspondence, and company rosters. This material was created by the association's executive committee, officers, and association members. Subseries A. By-laws includes by-laws and constitution articles of the association. Subseries B. Meeting Minutes includes record books, committee decisions, copies of general and special orders, and documents pertaining to the 1st Massachusetts Heavy Artillery monument. Subseries C. Company Rosters includes a notebook belonging to Joseph W. Gardner that compiles all members of the 1st Regiment Massachusetts Heavy Artillery. Member lists that record enlistment dates, discharge dates, birth and death dates, places of residence, and occupations before and after the war are also included. Subseries D. Correspondence includes correspondence, the majority of which is addressed to Secretary Gardner from association officers such as Stanley B. Dearborn, J. Payson Bradley, and William H. Morgan. Also included are letters from members of the association, which discuss annual reunions, deceased members of the regiment, and the overall state of the association.

Series II. Regiment History includes correspondence, personal anecdotes and narratives, reports on regimental movements, and surveys. This material was collection by Gardner and the Committee on Publication to help complete a regimental history. Subseries A. Correspondence includes correspondence written to Alfred S. Roe and Charles Nutt while each was working on the regiment history publication. Subseries B. Reports includes compiled notes on the movements and battles of the regiment. Subseries C. Personal Accounts includes surveys arranged by company that record member information, along with narratives written by members of the association that discuss recruiting, enlistment, company organization, and the various battles fought. The surveys were sent to members while the association was writing the regiment history and the narratives were requested at the same time. Two sketchbooks, letters, journals, discharge papers, and pension documents of regiment members along with transcripts of journals that date from the 1860s are included in this series.