ERS conducts research on local food systems, including alternative definitions of local food, estimates market size and reach, characteristics of local consumers and producers, and early indications of the economic and health impacts of local food systems. 

A 2015 ERS report provides the latest estimates on sales and farm participation in local food systems, the first analyses comparing prices between direct-to-consumer outlets and conventional grocery outlets, and local food farm growth and survival between 2007 and 2012. See:

Trends in U.S. Local and Regional Food Systems: A Report to Congress

For another comprehensive overview of local food systems, see:

Local Food Systems: Concepts, Impacts, and Issues