There are a number of places to get food in quantity for storage.In my part of the world:
I traveled to Idaho and found the mindset clearly focussed on preparation and survival. In fact I went to a couple of "Preparedness" stores and saw that even Walmart is in on the action.
I found a "Preparedness Center" at the local Walmart.It may be because of the fairly large LDS (Mormon) population in the area, however, it is interesting since "Preppers" and "Survivalists" outside the Rocky Mountain states probably don't see this in the Walmart stores in their areas. There are buckets of grains, canned goods, freeze-dried food items and blue water drums. Walmart isn't the only store I visited in my quest to stock up.
I stopped into the local "Army Surplus" store and it was like a kid in a candy store. So much I wanted but focussed mostly on my prep needs.
More Meals Ready to Eat (MRE) were on display as were the blue water drums. I bought six 55-gallon drums for one of my alternative E&E sites. I passed on the MREs as I personally prefer the freeze-dried foods with the indefinite shelf life. Next I went to Home Depot and got some shelve units that I set up and started to load with food and survival gear.