Although we may associate party stores with 40s and cigarettes, they do serve a more profound purpose. Michigan artist Thomas Rapai turned to party stores for a series of paintings that where shown at Chicago's 40000 Gallery in 2007:
“Nowhere Else To Go” presents a new body of drawings and paintings by Thomas Rapai. The artist continues his exploration into contemporary urbanity and kitsch; his brushy, colorful “Party Store” paintings mine modern art’s historical reference points.
Alluding to the documentary style of Ed Ruscha's “Gas Station” photography, as well as the architectural brushstrokes of Richard Diebenkorn, Rapai’s paintings embody something wholly Midwestern. The contextualizing of “Party Stores” (party store is Michigan slang for the corner convenience store) creates a romantic intention that immortalizes the ubiquitous corner store, where beer, chips, cigarettes and a quart of milk are always available.
And the Word Detective comments that the term is part of unique regional dialect:
Regional dialectical variations such as “party store” for what the rest of us call a “carry-out” or “convenience store” are common in the US. There’s even an organization dedicated to studying the phenomenon (the American Dialect Society) and an ongoing scholarly project, the Dictionary of American Regional English (DARE) cataloging local lingo in minute detail. Michigan shares many of the variations of what linguists call the Inland North along with Illinois, Indiana, Ohio and Wisconsin. Things get a bit weirder as you travel north in Michigan, where the residents of the Upper Peninsula (known as “Yoopers” from the initials UP) exhibit a vocabulary, phonological intonations and habits (especially ending sentences with “eh?”) more often associated with Canada.
Back at “party store,” I’d imagine the name arose because such places are where you buy the ingredients of an informal party, as opposed to the supermarket where one does “serious” food shopping (i.e., beyond beef jerky and cheese popcorn). In my ancestral home of New York City, such a little shop is known as a “bodega” (boh-DAY-guh), from the Spanish meaning “wine shop,” derived in turn from the Greek “apotheke,” store or depot, which also gave us “apothecary,” an old-fashioned name for a drugstore.