Meijer, pronounced à la Oscar Mayer [NOT "major" or "Meejer"], is a 'hypermarket' (think Target) chain of 195 stores located in the upper Midwest. The plurality of their stores are in Michigan, though stores are located in Illinois, Indiana, Ohio, and Kentucky. I've visited 14 Meijer locations.
A typical distribution of Meijer stores involves a "ring" along the circumferential highways around major cities. For example, here's their coverage of the Columbus, OH area:
No, this isn't meant as free advertising. Of interest to GP readers, each and every Meijer store has a Contract Postal Unit (CPU) at the customer service counter in the front of the store. It constitutes the largest CPU operation in the country. Most Meijer CPUs are open Sundays and many, like most of their parent stores, are operable 24 hours a day.
Most Meijer stores look the same; this is one of their stores outside Columbus, Ohio:
Each Meijer has a store number, and that store is #104. Here is a slightly older store design, outside Toledo.
In terms of postmark collecting: All Meijer CPUs have, at minimum, round daters akin to postmarks used at standard post offices around the country. They also are not obligated to assist philatelists in terms of postmarks as are classified POs. Results are mixed, ranging from friendly to highly restrictive. In some places the dater is locked away in the Store Director's office / vault due to security concerns, which to my knowledge should not be the case. Of the daters I have seen, some are the same as their local parent offices, and some are wonderful and unique.