The Biographical Directory of the United States Congress is a biographical dictionary of all present and former members of the United States Congress as well as its predecessor, the Continental Congress. Also included are Delegates from territories and the District of Columbia and Resident Commissioners from the Philippines and Puerto Rico. The on-line version goes well beyond the scope of the printed Biographical Directory to include images from the large photo collections of the Senate Historical Office and the Legislative Resource Center, additional information previously published in separate volumes (Guide to Research Collections of Former United States Senators Senators of the United States: a Historical Bibliography and Guide to Research Collections of Former Members of the House of Representatives), links to other sources of congressional information, and continuously updated entries that provide biographical information in clear and easy-to-read formats. Database searchable by name, state, position, party and year.

The Center for Legislative Archives, a part of the National Archives and Records Administration, preserves and makes available to researchers the historical records of the U.S. House of Representatives and the U.S. Senate.

Since 1920, the Clerk of the House has collected and published the official vote counts for federal elections from the official sources among the various states and territories.

GovInfo is a service of the United States Government Publishing Office (GPO). GovInfo provides free public access to official publications from all three branches of the Federal Government, including the Congressional Record, congressional committee materials, and congressional rules and procedures.

This site publishes the status of federal legislation, information about representative and senators in Congress including voting records, and original research on legislation. It also contains congressional roll call votes External from 1789 to the present.

"Discover the rich heritage of “the People’s House” and its central role in U.S. history since 1789. Explore the House's unique story and the individuals who have shaped it. Browse collections, access historical data, view documents, and listen to interviews." This site includes the "Résumés of Congressional Activity", which contains a comprehensive account of legislative business by the House of Representatives and the Senate from 1947 to the present. Also presented are "Party Divisions of the House of Representatives, 1789 to Present".

Historical information provided by the Senate Historical Office. Contains information on Senate powers and procedures, origins and foundations, traditions and symbols, historical highlights, and oral histories.

The Senate's the Virtual Reference Desk contains over 50 research guides providing information about a variety of topics ranging from Legislation, Senators, Committees, Senate Documents, and much more, including "Party Divisions from 1789 to the present".

The Brookings Institution presents the online edition of Vital Statistics on Congress. Vital Statistics’ purpose is to collect and provide useful data on America’s first branch of government, including data on the composition of its membership, its formal procedure (such as the use of the filibuster), informal norms, party structure, and staff.