Cityscape thumb|right|Old Harrisburg Post Office on the corner of Main and Church Street. thumb|left|Harrisburg square, 1950. At the beginning of the 20th century, Harrisburg prospered with one of the largest downtown districts in downstate Illinois.
Cityscape thumb|right|Old Harrisburg Post Office on the corner of Main and Church Street thumb|left|Harrisburg square 1950 At the beginning of the 20th century Harrisburg prospered with one of the largest downtown districts in downstate Illinois