Kennett Square Pennsylvania is knows as the mushroom capital of the world, and for good reason.  This area has been a hub of commercial mushroom cultivation for many decades.  Scenic Kennett Square, which is located just West of Philly, hosts an annual street fair to celebrate it's favorite agricultural crop, and if you've never been, it's well worth the trip.  It's so much fun(gi)!  

For your convenience, here's a link to the website for additional deets, and here is a fun(gi) video to tell you more.