The Law Librarians of Congress blog In Custodia Legis recently announced that Thomas.gov will officially retire as of July 5, 2016.
Thomas.gov was launched on January 5, 1995, after Congressional leadership directed the Library of Congress to make federal legislative information freely available to the public. On September 19, 2012 Congress.gov was introduced to eventually replace Thomas.gov with a more robust, updated system.
Congress.gov's beta label was removed in September 2014, and it is set to officially replace Thomas.gov as the official website for U.S. federal legislative information.
Congress.gov provides access to accurate, timely, and complete legislative information for Members of Congress, legislative agencies, and the public. It is presented by the Library of Congress (LOC) using data from the Office of the Clerk of the U.S. House of Representatives, the Office of the Secretary of the Senate, the Government Publishing Office, Congressional Budget Office, and the LOC's Congressional Research Service.