From the USDA Blog:
Did you know that the number of farms in the United States peaked in 1935 at 6,812,350 operations when the average farm size was 154.8 acres? In comparison, the 2007 Census of Agriculture counted 2,204,792 farms with the average farm size of 418 acres. In celebration of 150 years of service to American agriculture, the USDA’s National Agricultural Statistics Service (NASS), in partnership with Cornell University’s Mann Library, are making these and many other historical facts available online at http://agcensus.mannlib.cornell.edu
The Census of Agriculture reports contain aggregate data, on the county-, state- and national-level, for almost every facet of American agriculture, including number of farms, acres of farmland, totals for agricultural production, value of farm production, demographics and much more. The census reports are popular resources used by researchers, historians, genealogists, law professionals and others who want to know more about American agriculture and how the industry has expanded and changed over time.
Since 1840, the agricultural census has been conducted every five to 10 years. In 1997, USDA took over the responsibility for conducting the census from the Bureau of the Census and is currently conducted by NASS. The data collection procedures have changed significantly since the census of 1840. Today, agricultural data is collected through census report forms, which NASS mails out to prospective farm operators. In 2007, census respondents were able to complete the census report form online for the first time.
American agriculture and the tools used to conduct the census of agriculture have changed significantly since 1840. The historic census of agriculture reports, which were once only available through Federal Depository Libraries, are now accessible online for the first time.