From the USDA:
Three key features of U.S. agriculture highlight the importance of family farms. First, small family farms (those with less than $250,000 in annual sales) make up 88 percent of all U.S. farms. Second, large-scale family farms—about 10 percent of all farms—account for a disproportionately large, 72-percent share of the value of production. Third, farming is still an industry of family businesses. Nearly 98 percent of farms are family-owned, and they account for about 88 percent of production. Just over 2 percent of U.S farms are nonfamily farms, accounting for the remaining 12 percent of production.
