The U.S. Census is an excellent source of statistical information on the U.S. population, economy, and agriculture. Population census statistics are available from 1790-present and agriculture census statistics are available from 1840-present. Examples of Census resources from government and nongovernment providers include:
Decennial Census of Population and Housing 1790-2010 Features detailed population, economic, and agricultural data on the U.S. with breakdowns by state, counties, and communites.
Historical Census Data Browser 1790-1860 (Internet Archive version of former University of Virginia Libraries resource)
Historical Census of Agriculture 1840-2012 (Initially produced by the Census Bureau, this survey is now done every five years by the National Agricultural Statistics Service within the U.S. Dept. of Agriculture.
Historical Statistics of the United States (Purdue Users Only-Allows searching of U.S. Government statistics from the colonial era to 2000 and includes Confederate Government statistics.)
Prices & Wages by Decade (Courtesy: University of Missouri Library)