The records created and maintained within a Senator's office are the property of the member. Most Senators donate their collections to a research repository in their home state when they leave office. At the repository, the collections are made available to researchers after an appropriate amount of time has passed. Senatorial collections are valued by research libraries because they are rich sources for the study of local history, regional issues, national affairs, political science theory, foreign affairs, and public policy. While print and broadcast sources contain a great deal of congressional information, it is the Senator's personal papers that contain the most comprehensive and authentic record. Senators' papers are one of the two major sources (the other being records of Senate Committees) for documenting the legislative branch of government.

In general, Members' collections include correspondence, memos, reports, press releases, appointment calendars, speeches, voting records, electronic files, automated indexes and data bases, photographs, and taped interviews that document the legislative and constituent services work of a typical office. They may include information on personal and political activities, developing legislation, providing services to constituents, press relations and media activities, and basic office administration. Many collections include papers from family members and from Senators' pre- and post-Senate careers. Because of their breadth and coverage, they are valued as major primary resources for study of America's past.

Over 1,800 individuals have served in the United States Senate, and most are documented in personal collections. In addition, many papers can be found in the collections of their professional colleagues, other contemporaries such as journalists, and in the archives of professional organizations and associations. Approximately 600 publicly accessible research institutions across the country hold these collections. They include Members' personal papers, family papers, staff papers, correspondence with key individuals and organizations, and oral history interviews. Collectively, these materials document the lives and careers of former Senators, the legislative issues with which they dealt, and more generally, the legislative, political, and democratic processes of the United States Senate.