I mean at least on the West Coast of the US, my direct experience is that local farmers are selling at local grocers, that's where they sell most of their goods(that and to restaurants). Maybe not in Downtown SF or LA, but even in Davis or Sacramento for example, groceries are typically going to be locally sourced when they are in season.

This is because at the end of the day it benefits farmers and grocers to deal direct. Better produce, no middle man. Produce is very straight forward to sell by the pound too.