Whether large-scale or small farms dominate, a county's farm structure is influenced not only by changes within farming but also by key factors such as nonfarm economic activity, geography, and population growth. Large-farm counties where agriculture dominates the economy are concentrated in the Plains, Midwest, and Mississippi Delta. Small-farm counties, with larger, more diversified economic bases, are concentrated in the Southeast. However, more than 50% of the nation's counties are unclassified, presenting local planners with special challenges in charting development either toward agriculture or to a more diversified economic base. Unclassified counties that tend to have small-farm characteristics are found mostly in New England and scattered parts of the Southeast and West. Those tending to have large-farm characteristics are usually located adjacent to large-farm counties. This report identifies which counties are dominated by small- or large-farm agriculture as well as a large group, termed unclassified, which could go either way; provides models to differentiate county types; maps and describes developing subregions; and presents implications for rural America. (Author/NEC)