Cub, Rainbow, and Lund's/Byerly's had been the top three grocers in the Twin Cities, but recently non-unionized discount grocers have been moving in and making gains. Super Target, Aldi, and Walmart are all fairly new to the Twin Cities, but Super Target has already moved up to #2 and Walmart is #4.
Similar scenarios have happened before - "In the long run, though, this battle will drive someone out of business. That's always been true in the Twin Cities. The 1950s neighborhood grocers that grandma shopped gave way to Red Owl and Del-Farm, then Applebaum's and Country Club, then Cub and Rainbow."
Long time cashiers and Cub can make up to $22/hour, where at Super Target few make more than $10/hour.
Walmart has avoided the Twin Cities because of the union stronghold. They waited for other non-unionized businesses, such as Aldi and Target, to move in before following.
Discount stores are able to sell groceries like produce at below cost because they save on wages, benefits, and sell large amounts of non-perishables. Stores like Kowalski's are unable to do that because a large portion of their money is going to their employees.