The four blocks surrounding the courthouse form Rensselaer's Courthouse Square Historic District, listed on the National Register. Most of the buildings date from the boom years between 1880 and 1910, when the arrival of the railroad brought a brief surge of prosperity to the county seat.
The architecture is the standard small-town Indiana mix: brick Italianate fronts, decorative cornices, and pressed-tin ceilings inside many of the shops. The buildings have largely escaped redevelopment, and a slow walk around the square gives a fair sense of how a Midwestern county seat looked at the turn of the twentieth century.