Data.gov - "The purpose of Data.gov is to increase public access to high value, machine readable datasets generated by the Executive Branch of the Federal Government."
Fedstats - Provides easy access to statistics produced by more than 70 federal agencies. Allows access to Principal Federal Statistical Agencies.
Health Data Interactive (CDC) - A selection of national health statistics.
Historical Census Files 1790- (Census Bureau)
Historical Census Publications (Univ. of Michigan)
IPUMS USA (Minnesota Population Center) - Integrated Public Use Microdata Series from U.S. Census data, 1790-
National Historical Geographic Information System (NHGIS) - Aggregate historical census data, 1790-Present.
Social Explorer - Interactive historical data maps with selected data back to 1790.
ProQuest Statistical Insight - An index to over 100,000 statistical publications with links to the full- text of selected publications and web sites.
Tax Statistics (IRS) - Provides tables, articles, and data from the U.S. tax system.
Statistics on Veterans (VA) - Provides data related to veterans.
Migration Data - Migration patterns by state or by county for the entire United States.
Vital Statistics (National Center for Health Statistics)
Factsheets - quick popular facts about communities (US, states, counties, cities towns, and 5-digit ZIP Codes). Fact Sheets include information on people, housing, business & government.
DataSets - provides summary and detailed tables by geography, and demographic and housing characteristics for 100 percent and sample data.
Census 2000 Demographic Profiles
DP-1/General Demographic Characteristics
DP-2/Selected Social characteristics
DP-3/Selected economic characteristics
DP-4/Selected housing characteristics
Other options for data by County: