There were 312 growers of agaricus and specialty mushrooms in the United States in the 2009-2010 growing season. Today’s market size is the estimated value of their crop of agaricus and specialty mushrooms. The State of Pennsylvania was the leading state for this crop with a 49.56% share of the total crop. California was the next largest producing state with a 20.78% share and Washington was the third largest with a 2.48% share.

Geographic reference: United States
Year: 2009-2010 Season
Market size: $924.86 million
Source: “Mushrooms,” one in a series of crop reports produced by the U.S. Department of Agriculture, last updated on August 19, 2010. Here is a link to the USDA report on mushrooms.
Original source: U.S. Agriculture Department (USDA)