The primary source for this exercise and a great resource for
further
analysis is the 1992 Agricultural Atlas of the United States provided
on-line by the U. S. Department of Agriculture at the following URL:
http://www.nass.usda.gov/census/census92/atlas92/html/index.htm.
The 1997 Agricultural Atlas of the United States has
recently
been made available on the WWW at this URL:
http://www.nass.usda.gov/census/census97/atlas97/menu.htm.
The National Agricultural Statistics Service (U.S. Dept. of
Agriculture) maintains a website of the Census of Agriculture
(conducted in years that end in two and seven) and the most recent data
can be found there: http://www.nass.usda.gov/Census_of_Agriculture/index.asp.
Another useful website with a good set of links about agricultural geography is the Agricultural Geography section of the Geography page at About.com. It's URL is: http://geography.about.com/msub28.htm?pid=2820&cob=home.