The Lee H. Hamilton Congressional papers are a selection from the approximately 3500 cartons of records generated during his 34-year tenure in the House of Representatives. The contents of the collection, chosen by his staff in consultation with the manuscripts curator of the Lilly Library, illustrate the multiple roles of a model Congressman, i.e. local representative and constituent advocate, represented in the Legislative and Constituent Services series; national legislator and consensus builder, reflected in the Legislative series; educator, evident in the Public Communications series; committee member, reflected in his impressive record of committee service but particularly in the Committee on Foreign Affairs series; and investigator, again evident in his committee service but with special emphasis in the series on the Iran-Contra investigation of 1987.

A major strength of the collection lies in its portrayal of Hamilton's consistently strong record of service to his constituents both in projects of many kinds throughout the 9th district and his emphasis on personalized responses to constituent correspondence that by 1989 was numbering close to 30,000 letters a year. He developed his positions on legislative issues in part through his substantive responses to those correspondents, which are to be found in the Legislative Mail and Issues Files subseries. The mechanisms through which that level of communication was maintained are evident in the Alphas and Form Letters subseries, the Schedule Files, and the Weekly Reports, all in the Office Administration series. The Schedule Files in the Office Administration series are a rich resource for his face-to-face contacts with constituents. The content of Hamilton's side of the dialogue is richly represented in his weekly Washington Reports newsletters, Mailings, and Speeches in the Public Communications series as well as in the Extensions of Remarks and Statements subseries of the Legislative series. The Washington Reports will eventually be available in digital form through this finding aid, as will his Foreign Affairs Newsletters and other digitized documents in the collection. As of February 2022 these can only be accessed through a prior version of this finding aid.

Resources for studying constituent positions are likewise quite plentiful, particularly for the early 1970s, for which there are nearly 34 linear feet of letters on specific legislation as well as local, national, and international issues of concern. Letters on the possible impeachment of Nixon, the energy crisis, and such continuing issues as abortion and drugs are particularly abundant.

The Projects subseries of the Constituent Services series offers particular potential for research because of both its extent and because of the abundance of records in certain portions of the subseries. The threat of base closures hovered over nearly the full span of Hamilton's career, with the consequent economic displacement and environmental problems. The records for the Jefferson Proving Ground in particular (7.5 linear feet), as well as for the Bakalar Air Force Base, the Indiana Army Ammunition Plant, and the Naval Ordnance Station in Louisville, trace not only Hamilton's efforts but the mobilization of local initiatives to exert pressure on numerous parts of the federal bureaucracy in order to humanize the process and the ultimate disposition of those installations. Broader coverage is available in other portions of the Projects files, supplemented by the files on Indiana Projects and Issues from the 1980s, found in the Research-News Clippings 1979-1986 subseries of the Constituent Services series. The Projects subseries also offers abundant resources for researching the specific environmental issues associated with flood control, watersheds, Ohio River development and pollution, nuclear power, and the pollution of unexploded ordnance at the Jefferson Proving Ground. There are also abundant resources on the evolution of proposals for the Hoosier National Forest and the Muscatatuck Wildlife Refuge in the Wilderness records of the Projects subseries.

Another strength of the collection lies in its reflection of Hamilton's emphasis on the integrity of the institution of Congress and its constitutional role, to be found in his work with the Commission on Administrative Review, the Committee on Standards of Official Conduct, and the Joint Committee on the Organization of Congress, and throughout his career in his work with the Committee on Foreign Affairs, as he built the foundations for a more active congressional role in the formulation of foreign policy. The records relating to the Committee on Foreign Affairs are an additional strength of the collection and will become more so over time as they are opened. The photocopies of official correspondence and memoranda are governed by House of Representatives Rule VII, which restricts access to them until 30 years from date of creation. Also of interest are the files relating to the hearings of the House Select Committee to Investigate Covert Arms Transactions with Iran (Iran-Contra), for which there is a daily record of journalistic coverage from the New York Times, the Washington Post, and the Christian Science Monitor as well as hearings materials in both preliminary and printed form.