U.S. Government Documents
U.S. Government documents are excellent resources for studying the 1970s. The U.S. Government is the world's largest publisher producing information on a variety of topics. Purdue is one of over 1,200 U.S. federal depository libraries and general information about these resources can be found here which also features research guides for finding government information on various topics.
Government Information Indexes
Monthly Catalog of U.S. Government Publications HSSE Periodicals 016.353 Un36 and its online version covers from July 1976-present with many recent documents being full text online.
Congressional Information Service (CIS) Index HSSE REF & 2nd floor periodical stacks 328.73005 C76 (Indexes U.S. Congressional Committee hearings.)
Historic U.S. Census of Population 1790-2010 (Excellent resources for analyzing population, social, and economic trends and developments.)
Local Climatological Data (Weather reports for selected U.S. locations.)
U.S. Army Center for Military History PublicationsHSSE DOC D 114 (Excellent source for military history information.)
Secretary of Defense Historical Office (Histories of this office and weapons systems, plus annual DOD reports)
Foreign Relations of the United States HSSE Periodicals 327.73 Un32 This State Department resource is the official U.S. foreign policy documentary collection. Nixon and Ford Administration volumes now being published along with some Carter Administration volumes)
FBI Freedom of Information Act (Features FBI files on numerous prominent individuals including Lucille Ball, Elvis Presley, Frank Sinatra, and others.)
Central Intelligence Agency FOIA (Features access to declasified National Intelligence Estimates on various countries and regions. Select "Special Collections" then "National Intelligence Council (NIC) Collection" once you connect to this site.)
Hathitrust Catalog-Provides access to the full text of many historic U.S. Government documents through a collaboration between many university research libraries and Google.
Nixon Grand Jury Records-Features transcripts of June 23-24, 1975 grand jury interviews with Richard Nixon over Watergate related matters.