Congressional Primary 
Sources

US Serial Set Digital Edition  UIUC
The US Serial Set, which consists of congressional reports and documents, is a 15,000-volume resource of enormous breadth.  A congressional report is a committee's report on a bill it has considered and is usually issued only if the committee views the legislation favorably.  Congressional documents are much more varied, including proceedings, the House and Senate journals, and many other types of publications.

Printed Congressional Proceedings  

• Congressional Record
  Q.328.731 Un34  1873-  MAIN STACKS

• Congressional Globe
  MFICHE KF34.6  1833-1873  LAW LIBRARY  

• Debates and Proceedings in the Congress of the United States
  328.731 Un3  1789-1824  MAIN STACKS

Statutes

United States Statutes at Large
DOC.GS4.111:  1789-1983  GDL
Contains every law passed by the U.S. government.  They are arranged chronologically.

Shepard's Acts and Cases by Popular Names: Federal and State
345 Sh45  GDL
Use as a bridge to get from the popular name of a law to the law itself as printed in United States Statutes at Large, which is organized by public law number.  "P.L. " (or P.L. 34-1), for example, is the public law number for the first law passed in the 34th congress. 

Other Tools 

Congressional Information for Historians  
Use this to identify the indexes you should use for particular periods.
 

Catalogs 
and 
Indexes

General Indexes

LexisNexis Congressional  UIUC
Search the Historical Indexes on this resource's home page.  Subject searches are the most precise.  Searches by "witness" lead to testimony given before House and Senate committees.

Comprehensive Index to the Publications of the United States Government, 1881-1893.
015.73 Un312 1953  GDL

Cumulative Index to Hickcox's Monthly Catalog of United States Government Publications, 1885-1894.  3 vols. 
015.73 H524u index  GDL
Serves as a comprehensive, user-friendly index to U.S. Government documents abstracted in the Monthly Catalog of U.S. Government Publications.

Monthly Catalog of U.S. Government Publications
015.73 UN35 1895-  GDL  
This is the most complete index to U.S. government documents issued from 1895 to the present day.  Only the most recent years are available online.

Indexes to Congressional Documents

CIS U.S. Serial Set Index, 1789-1969
015.73 C759  GDL
Indexes the 15,000 volumes--and more than 325,000 individual documents--of the U.S. Serial Set.  The index provides subject and keyword access.  Note that volumes 2,817 to 13,914 can be found on Deck 1 East of the Main Stacks in print format.  Other volumes are available in digital format and/or on microfiche in the Government Documents Library.

Statistics

Census of the United States, 1790-  (Arranged chronologically on the east wall of the GDL; the earliest volumes can be found in a low metal bookcase near the microfiche reader/printers.)
This is the U.S. government's premier source of demographic and economic data on the United States.

Historical Census Browser (University of Virginia)
Provides extensive census data at the national, state, and county levels.  The quantity of data found here varies considerably from one census to another, and only a small percentage of the statistics--and little of the text--found in the printed volumes are available through this resource.

Selected Historical Decennial Census: Population and Housing Counts
Provides mainly demographic data.  More information is available on states and the nation than on smaller geographic entities.

Statistical Abstract of the United States
DOC. C3.134:  1879-  MAIN STACKS
The Statistical Abstract is the broadest statistical source of the U.S. government.  It draws heavily from the decennial censuses.

LexisNexis Statistical  UIUC  
This database consists of tables in the form of PDF files.  Use the Subject List to ensure that your search results are complete and lacking false hits.  More importantly, restrict your search to U.S. resources and identify the period that interests you.
 

National Archives  
Use the Subject Index at the top of the page and, perhaps more importantly, the Online Research Tools whose links appear in the middle of the screen as you scroll down.  The two most important are the Archival Research Catalog (ARC) and the Guide to Federal Records.  The latter identifies the record groups that are available and gives its location(s).  Contact staff of the National Archives and Records Administration (NARA) through their site; they are very responsive, especially when you demonstrate that you've taken your search as far as possible using the resources at hand.

American Memory
This is a gateway to U.S. historical materials digitized by the Library of Congress.  It is organized into more than 100 thematic collections that can be browsed by subject, period, medium, or location.

Miscellaneous 

CQ Voting and Elections Collection  UIUC
The CQ Voting and Elections Collection brings together a wealth of statistical data, analysis, and historical material.  It covers major and minor political parties, candidates, and so on.  An associated database on election results is also part of this resource.