That’s because the incorporated area of the Town of Harrington is quite small.
The State Fairgrounds and Casino are actually located outside the town limits.
When we say “Harrington” it refers to the town and the surrounding area, not only to the town itself.
In Indiana you have townships, which are much larger, because your state was settled much later.
The Town of Georgetown, which I lived in for nine years here, has a population of 6,400, and an area of 4.1 square miles.
Roughly 2x the size of Harrington. Same population density.
That makes sense. We have a walking trail from the middle of our fairground to the edge of town it is one mile. Included in that area is a race track , the jail , juvenile center, county garage and a dozen or so houses. No way all those 3,000+ people and everything else listed could fit. Wiki sometimes makes mistakes so I figured someone had confused 2 sq miles with 2 miles sq.
It is the most common mistake on standardized tests !