USDA Census of Agriculture (link below): "The Census of Agriculture is a complete count of U.S. farms and ranches and the people who operate them. Even small plots of land - whether rural or urban - growing fruit, vegetables or some food animals count if $1,000 or more of such products were raised and sold, or normally would have been sold, during the Census year. The Census of Agriculture, taken only once every five years, looks at land use and ownership, operator characteristics, production practices, income and expenditures."
Before the US Department of Agriculture (USDA) took over the Census of Agriculture, it was conducted by the Census Bureau.