With my mom involved in several facets of the community and my dad involved in cycling, the dog sled races, the local paper, and the local news station while he was there, I grew up enmeshed in a small town, even though Quesnel has all of thirty thousand people.
For me, this led to several important facts, in no particular order:
-I have ridden a draft horse.
-I have been outside in -52 degrees Celsius
-I never want to be outside in -52 degrees Celsius ever again
-I can name five types of salmon off the top of my head
-I pay attention, in stories, to how sensibly a city is brought about.
This is especially important in speculative fiction and fantasy, where the worlds are more likely to be completely separate from our own, but also in literary or mainstream fiction. If your city is in the middle of a desert, with no obvious water supply, it will ruin the whole story for me. If your small town is surrounded by impassable mountains and no one could get in until a tunnel was blasted through and there is no apparent wealth (mineral or vegetable or animal) there, why does anyone live there in the first place?
Similarly, how does the town run? In large cities, this can be mostly excused, as they find ways to perpetuate long after the original reason is gone. In small towns, though, where a single industry can be the beating heart of the town, what is the industry? Does it have one? Having also spent time in the Midwest, I'll accept farming as an answer, now, though grudgingly.