The papers of Gideon Welles (1802-1878) span the period 1777-1911, with the core of the material concentrated in the years 1820-1878. The papers include diaries, correspondence, writings, naval records, and scrapbooks reflecting all phases of Welles's career as a newspaper editor, politician, and naval administrator. Welles was a gifted diarist, correspondent, and essayist, and his papers are a rich source of primary materials for the study of the political and social history of the United States in the nineteenth century.

The Diaries series includes a fifteen-volume diary, 1862-1869, written when Welles was secretary of the navy, and a three-volume retrospective narrative, 1861-1869, plus notes and journal entries for earlier periods in his life. Welles's Civil War diaries were excerpted and edited by his son, Edgar Thaddeus Welles, for publication in a three-volume set in 1911, drafts of which are also included in the series.

Documentation for Welles's political, literary, and personal endeavors is distributed throughout the collection. Welles's administration of the navy is most substantially documented in his diaries and in the series of official letterbooks. His diaries contain observations about cabinet members during the administrations of Abraham Lincoln and Andrew Johnson. The Letterbooks record the day-to-day operational and administrative policies enacted by the Navy Department during the Civil War including those related to the establishment of blockades, ship construction and naval ordnance, the outfitting of ironclads, naval engagements and tactical maneuvers, and the pursuit and capture of Confederate cruisers and subsequent rewarding of prize money.

In addition to the Diaries and Letterbooks, the papers also include a series of Navy Department records collected by Edgar Thaddeus Welles while he was employed as chief clerk of the Navy Department, 1865-1869. The records are mostly concerned with routine administrative detail, especially solicitations for positions and appointments of clerks, midshipmen, surgeon's mates, and other minor officials.

The Diaries also document Welles's literary ambitions, evident even in his youth. He attended Cheshire Episcopal Academy and the newly founded Literary, Scientific and Military Academy in Norwich, Vermont. While enrolled at the latter school, Welles drafted one of his earliest writings entitled "Journal of an Excursion to the White Mountains," an account of a field trip undertaken by Welles and fifty other students in 1824 under the leadership of Alden Partridge, headmaster and founder of the academy. The draft of this journal is included in his diary and another copy is located in the Speeches and Writings file. Exclusive of his Civil War entries, the remainder of the diaries include occasional drafts of prose and poetry, meditations in essay form, drafts of letters, travel descriptions, and entries recording Welles's keen interest in observing the political and natural world around him. The correspondence series also contains material relating to Welles's school years and letters exchanged with family members, friends, and schoolmates from Cheshire and Norwich.

Welles was a lifelong adherent to Jeffersonian principles and, until his departure in 1854, an active participant in the Democratic party. As a writer and politician, he helped organize and promote Jacksonian democracy in his home state of Connecticut through the editorial policy of his newspaper, the Hartford Times , and through his involvement as a Democratic party spokesman and state legislator. The Correspondence series is composed primarily of political correspondence documenting Welles's commitment to the principles of Jefferson and Jackson on both statewide and national levels first as a member of the Democratic party and then in the newly-established Republican party. Welles's correspondence with Democratic party leaders and functionaries concerns the party from Jackson's administration to that of Franklin Pierce. Letters in the Miscellany series written to Welles by John M. Niles, senator from Connecticut, 1835-1839 and 1843-1849, and postmaster general, 1840-1841, provide detailed accounts of personalities and political issues.

The Correspondence series further chronicles Welles's withdrawal from the Democratic party in 1854 over the issue of slavery and the development of the Republican party. Other correspondence dates from his term of office as secretary of the navy throughout the Civil War and the early years of Reconstruction.

Observations of a more personal or family nature are interwoven throughout the correspondence. Welles's letters to his cousin, R. C. Hale, 1833-1835, were written while he was courting Hale's sister and Welles's future wife, Mary Hale.

As an editorial writer and journalist, Welles contributed many articles on local and national politics to the Hartford Times and, after his retirement in 1869, to the Galaxy . The Speeches and Writings series contains copies of many of these articles, and material in the Correspondence series reveals interaction between newspaper policy and politics in nineteenth century America.

A Miscellany series includes correspondence files for Welles's longtime political ally and personal friend, John M. Niles, as well as for Welles's wife Mary and son, Edgar Thaddeus. The Henry B. Learned series contains research material relating to Welles compiled in the course of Learned's research on the executive branch of government.

A partial index to the correspondence is arranged alphabetically by correspondent and identifies items in the Correspondence series, the Records of the Navy Department, and the correspondence files of John M. Niles, Edgar Thaddeus Welles, and Mary Hale Welles. It also lists correspondents other than Gideon Welles in the Miscellany series for the inclusive dates 1 January 1777-25 February 1828 and 14 March 1860-19 January 1911. Correspondents include Joseph Pratt Allyn, James F. Babcock, Montgomery Blair, Alfred Edmund Burr, Salmon P. Chase, Edward Spicer Cleveland, John Adolphus Bernard Dahlgren, Calvin Day, James Dixon, James Buchanan Eads, Henry H. Elliot, Andrew H. Foote, John Murray Forbes, Joseph R. Hawley, Mark Howard, Amasa Jackson, Thornton A. Jenkins, Richard M. Johnson, James E. Jouett, Andrew T. Judson, Henry Mitchell, Edwin D. Morgan, Nathaniel Niles, William Patton, Hiram Paulding, J.J.R. Pease, William V. Pettit, James J. Pratt, Albert Smith, Sylvester S. Southworth, Daniel D. Tompkins, Charles Wilkes.

The Additions include correspondence to and from Welles, 1822-1877, letters relating to Welles, and undated drafts of his writings covering a wide range of personal, business, and political subjects, especially naval matters, the Civil War, and Reconstruction policies. In Addition I, the letters and writings concern political parties and presidential candidates and questions on the limits and uses of federal and state powers. A few items date from Welles's youth in Connecticut or concern his early interest in local politics. Correspondents include Schuyler Colfax, Samuel Sullivan Cox, Charles A. Dana, John A. Dix, William Faxon, Orris S. Ferry, David Dudley Field (1805-1894), Gustavus Vasa Fox, Foxhall A. Parker, Joseph Smith, Charles Dudley Warner, and Thurlow Weed. Addition II includes a draft of his 1874 book Lincoln and Seward as well as notes and draft writings for a series of articles for Galaxy magazine that formed the basis of the 1874 book. Addition II also contains a letter by Welles to Orville H. Browning relating to William Henry Seward and to a history being written by Thurlow Weed. The Additions have not been microfilmed or indexed.