I live in the heart of mushroom farming/industry near Kennett Square, PA; which claims to be the producer of more mushrooms than anywhere in the universe.
Its a different kind of farming, taking place all indoors and it goes on all year round, harvesting daily except Christmas, 364 days a year.
They are grown in sheds made of cinderblock that are climate controlled and contain shelf upon shelf of trays of growing spawn.
One of the reasons for the concentration around KS is that t he support industries are all right there and can cheaply service multiple operations. Biggest of them are the companies who make mushroom soil which is a mixture of various plants and a bit of manure that get composted for months. Before mushrooms see it it is pasteurized to remove any remnants of poo bacteria. The result is a black loamy product that the fungi adore, but is too rich for many plants. If you want to spread spent mushroom soil on your lawn it must age for a few months in the rain to cool it down lest it burn your grass.
The composting used to smell horrible if the wind blew the wrong way, but they've gotten the stink out of it somehow.
Besides the growers and suppliers there are the packers, like this place who kindly has a fridge full of ultra fresh fungi for sale to civilians at great prices.