Some further background information.
As the business became more successful after the Depression they wanted to present a stylish and unified presence to their customers so they hired the Architect Harry Weese to design a “Modern Grocery Store” for them. The company wanted something simple yet stylish to show the customer that the business was not constructing an expensively ornate building and passing the cost on to the consumer. At the same time the building needed to function as a grocery store and entice the consumer to shop.
Now Harry Weese was no slouch as an Architect, he had designed the Washington D.C. Metro Station among other notable structures. He came up with an idea to use what they call the Art Moderne style. This style represents the movement away from pre-Depression designs that favored ornamentation. Stylistic elements of Art Moderne emphasize curving forms, long lines, metal windows, and smooth wall finishes.
Weese’s design used a barrel truss roof system that we equate to a Quonset Hut, although his design pre-dated the military Quonset hut by several years. This design became the signature of Purity Stores from that point forward to this day.
The elliptic arch design can be seen in this banner ad, I think that this was the original Weese design for the stores
This banner ad shows a modified elliptic arch with “shoulders”, this ad is dated 1946 thus indicating a more “modern” design or upgrade to the store design. Perhaps this change allowed for more usable floor space and additional natural lighting but who knows?